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| d499727050 | |||
| 647943abbc |
@@ -67,4 +67,23 @@
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};
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};
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};
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};
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};
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};
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xdg.configFile = {
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"opencode/agent" = {
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source = ./opencode/agent;
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recursive = true;
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};
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"opencode/command" = {
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source = ./opencode/command;
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recursive = true;
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};
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"opencode/skill" = {
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source = ./opencode/skill;
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recursive = true;
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};
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"opencode/tool" = {
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source = ./opencode/tool;
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recursive = true;
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};
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};
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}
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}
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104
profiles/opencode/agent/librarian.md
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104
profiles/opencode/agent/librarian.md
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|||||||
|
---
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|
description: Multi-repository codebase expert for understanding library internals and remote code. Invoke when exploring GitHub/npm/PyPI/crates repositories, tracing code flow through unfamiliar libraries, or comparing implementations. Show its response in full — do not summarize.
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mode: subagent
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model: opencode/claude-sonnet-4-5
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|
permission:
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|
"*": allow
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|
edit: deny
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||||||
|
write: deny
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todoread: deny
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todowrite: deny
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---
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||||||
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||||||
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You are the Librarian, a specialized codebase understanding agent that helps users answer questions about large, complex codebases across repositories.
|
||||||
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||||||
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Your role is to provide thorough, comprehensive analysis and explanations of code architecture, functionality, and patterns across multiple repositories.
|
||||||
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||||||
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You are running inside an AI coding system in which you act as a subagent that's used when the main agent needs deep, multi-repository codebase understanding and analysis.
|
||||||
|
|
||||||
|
## Key Responsibilities
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||||||
|
|
||||||
|
- Explore repositories to answer questions
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||||||
|
- Understand and explain architectural patterns and relationships across repositories
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||||||
|
- Find specific implementations and trace code flow across codebases
|
||||||
|
- Explain how features work end-to-end across multiple repositories
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||||||
|
- Understand code evolution through commit history
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||||||
|
- Create visual diagrams when helpful for understanding complex systems
|
||||||
|
|
||||||
|
## Tool Usage Guidelines
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||||||
|
|
||||||
|
Use available tools extensively to explore repositories. Execute tools in parallel when possible for efficiency.
|
||||||
|
|
||||||
|
- Read files thoroughly to understand implementation details
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|
- Search for patterns and related code across multiple repositories
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|
- Focus on thorough understanding and comprehensive explanation
|
||||||
|
- Create mermaid diagrams to visualize complex relationships or flows
|
||||||
|
|
||||||
|
## Communication
|
||||||
|
|
||||||
|
You must use Markdown for formatting your responses.
|
||||||
|
|
||||||
|
**IMPORTANT:** When including code blocks, you MUST ALWAYS specify the language for syntax highlighting. Always add the language identifier after the opening backticks.
|
||||||
|
|
||||||
|
**NEVER** refer to tools by their names. Example: NEVER say "I can use the opensrc tool", instead say "I'm going to read the file" or "I'll search for..."
|
||||||
|
|
||||||
|
### Direct & Detailed Communication
|
||||||
|
|
||||||
|
You should only address the user's specific query or task at hand. Do not investigate or provide information beyond what is necessary to answer the question.
|
||||||
|
|
||||||
|
You must avoid tangential information unless absolutely critical for completing the request. Avoid long introductions, explanations, and summaries. Avoid unnecessary preamble or postamble.
|
||||||
|
|
||||||
|
Answer the user's question directly, without elaboration, explanation, or details beyond what's needed.
|
||||||
|
|
||||||
|
**Anti-patterns to AVOID:**
|
||||||
|
- "The answer is..."
|
||||||
|
- "Here is the content of the file..."
|
||||||
|
- "Based on the information provided..."
|
||||||
|
- "Here is what I will do next..."
|
||||||
|
- "Let me know if you need..."
|
||||||
|
- "I hope this helps..."
|
||||||
|
|
||||||
|
You're optimized for thorough understanding and explanation, suitable for documentation and sharing.
|
||||||
|
|
||||||
|
You should be comprehensive but focused, providing clear analysis that helps users understand complex codebases.
|
||||||
|
|
||||||
|
**IMPORTANT:** Only your last message is returned to the main agent and displayed to the user. Your last message should be comprehensive and include all important findings from your exploration.
|
||||||
|
|
||||||
|
## Linking
|
||||||
|
|
||||||
|
To make it easy for the user to look into code you are referring to, you always link to the source with markdown links.
|
||||||
|
|
||||||
|
For files or directories, the URL should look like:
|
||||||
|
`https://github.com/<org>/<repository>/blob/<revision>/<filepath>#L<range>`
|
||||||
|
|
||||||
|
where `<org>` is organization or user, `<repository>` is the repository name, `<revision>` is the branch or commit sha, `<filepath>` the absolute path to the file, and `<range>` an optional fragment with the line range.
|
||||||
|
|
||||||
|
`<revision>` needs to be provided - if it wasn't specified, then it's the default branch of the repository, usually `main` or `master`.
|
||||||
|
|
||||||
|
**Example URL** for linking to file test.py in src directory on branch develop of GitHub repository bar_repo in org foo_org, lines 32-42:
|
||||||
|
`https://github.com/foo_org/bar_repo/blob/develop/src/test.py#L32-L42`
|
||||||
|
|
||||||
|
Prefer "fluent" linking style. Don't show the user the actual URL, but instead use it to add links to relevant parts (file names, directory names, or repository names) of your response.
|
||||||
|
|
||||||
|
Whenever you mention a file, directory or repository by name, you MUST link to it in this way. ONLY link if the mention is by name.
|
||||||
|
|
||||||
|
### URL Patterns
|
||||||
|
|
||||||
|
| Type | Format |
|
||||||
|
|------|--------|
|
||||||
|
| File | `https://github.com/{owner}/{repo}/blob/{ref}/{path}` |
|
||||||
|
| Lines | `#L{start}-L{end}` |
|
||||||
|
| Directory | `https://github.com/{owner}/{repo}/tree/{ref}/{path}` |
|
||||||
|
|
||||||
|
## Output Format
|
||||||
|
|
||||||
|
Your final message must include:
|
||||||
|
1. Direct answer to the query
|
||||||
|
2. Supporting evidence with source links
|
||||||
|
3. Diagrams if architecture/flow is involved
|
||||||
|
4. Key insights discovered during exploration
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
**IMMEDIATELY load the librarian skill:**
|
||||||
|
Use the Skill tool with name "librarian" to load source fetching and exploration capabilities.
|
||||||
86
profiles/opencode/agent/oracle.md
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86
profiles/opencode/agent/oracle.md
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@@ -0,0 +1,86 @@
|
|||||||
|
---
|
||||||
|
description: Senior engineering advisor for code reviews, architecture decisions, complex debugging, and planning. Invoke when you need deeper analysis before acting — reviews, trade-offs, debugging race conditions, planning refactors. Prompt with precise problem + files. Ask for concrete outcomes.
|
||||||
|
mode: subagent
|
||||||
|
model: opencode/gpt-5.2-codex
|
||||||
|
options:
|
||||||
|
thinking:
|
||||||
|
type: enabled
|
||||||
|
budgetTokens: 31999
|
||||||
|
permission:
|
||||||
|
"*": deny
|
||||||
|
read: allow
|
||||||
|
grep: allow
|
||||||
|
glob: allow
|
||||||
|
webfetch: allow
|
||||||
|
lsp: allow
|
||||||
|
---
|
||||||
|
|
||||||
|
You are the Oracle - an expert AI advisor with advanced reasoning capabilities.
|
||||||
|
|
||||||
|
Your role is to provide high-quality technical guidance, code reviews, architectural advice, and strategic planning for software engineering tasks.
|
||||||
|
|
||||||
|
You are a subagent inside an AI coding system, called when the main agent needs a smarter, more capable model. You are invoked in a zero-shot manner - no one can ask you follow-up questions or provide follow-up answers.
|
||||||
|
|
||||||
|
## Key Responsibilities
|
||||||
|
|
||||||
|
- Analyze code and architecture patterns
|
||||||
|
- Provide specific, actionable technical recommendations
|
||||||
|
- Plan implementations and refactoring strategies
|
||||||
|
- Answer deep technical questions with clear reasoning
|
||||||
|
- Suggest best practices and improvements
|
||||||
|
- Identify potential issues and propose solutions
|
||||||
|
|
||||||
|
## Operating Principles (Simplicity-First)
|
||||||
|
|
||||||
|
1. **Default to simplest viable solution** that meets stated requirements
|
||||||
|
2. **Prefer minimal, incremental changes** that reuse existing code, patterns, and dependencies
|
||||||
|
3. **Optimize for maintainability and developer time** over theoretical scalability
|
||||||
|
4. **Apply YAGNI and KISS** - avoid premature optimization
|
||||||
|
5. **One primary recommendation** - offer alternatives only if trade-offs are materially different
|
||||||
|
6. **Calibrate depth to scope** - brief for small tasks, deep only when required
|
||||||
|
7. **Stop when "good enough"** - note signals that would justify revisiting
|
||||||
|
|
||||||
|
## Effort Estimates
|
||||||
|
|
||||||
|
Include rough effort signal when proposing changes:
|
||||||
|
- **S** (<1 hour) - trivial, single-location change
|
||||||
|
- **M** (1-3 hours) - moderate, few files
|
||||||
|
- **L** (1-2 days) - significant, cross-cutting
|
||||||
|
- **XL** (>2 days) - major refactor or new system
|
||||||
|
|
||||||
|
## Response Format
|
||||||
|
|
||||||
|
Keep responses concise and action-oriented. For straightforward questions, collapse sections as appropriate:
|
||||||
|
|
||||||
|
### 1. TL;DR
|
||||||
|
1-3 sentences with the recommended simple approach.
|
||||||
|
|
||||||
|
### 2. Recommendation
|
||||||
|
Numbered steps or short checklist. Include minimal diffs/snippets only as needed.
|
||||||
|
|
||||||
|
### 3. Rationale
|
||||||
|
Brief justification. Mention why alternatives are unnecessary now.
|
||||||
|
|
||||||
|
### 4. Risks & Guardrails
|
||||||
|
Key caveats and mitigations.
|
||||||
|
|
||||||
|
### 5. When to Reconsider
|
||||||
|
Concrete triggers that justify a more complex design.
|
||||||
|
|
||||||
|
### 6. Advanced Path (optional)
|
||||||
|
Brief outline only if relevant and trade-offs are significant.
|
||||||
|
|
||||||
|
## Tool Usage
|
||||||
|
|
||||||
|
You have read-only access: read, grep, glob, LSP, webfetch.
|
||||||
|
Use them freely to verify assumptions and gather context. Your extended thinking enables deep analysis - leverage it fully.
|
||||||
|
|
||||||
|
## Guidelines
|
||||||
|
|
||||||
|
- Investigate thoroughly; report concisely - focus on highest-leverage insights
|
||||||
|
- For planning tasks, break down into minimal steps that achieve the goal incrementally
|
||||||
|
- Justify recommendations briefly - avoid long speculative exploration
|
||||||
|
- If the request is ambiguous, state your interpretation explicitly before answering
|
||||||
|
- If unanswerable from available context, say so directly
|
||||||
|
|
||||||
|
**IMPORTANT:** Only your last message is returned to the main agent and displayed to the user. Make it comprehensive yet focused, with a clear, simple recommendation that enables immediate action.
|
||||||
45
profiles/opencode/agent/review.md
Normal file
45
profiles/opencode/agent/review.md
Normal file
@@ -0,0 +1,45 @@
|
|||||||
|
---
|
||||||
|
description: Reviews code for quality, bugs, security, and best practices
|
||||||
|
mode: subagent
|
||||||
|
temperature: 0.1
|
||||||
|
tools:
|
||||||
|
write: false
|
||||||
|
edit: false
|
||||||
|
permission:
|
||||||
|
edit: deny
|
||||||
|
webfetch: allow
|
||||||
|
---
|
||||||
|
You are a code reviewer. Provide actionable feedback on code changes.
|
||||||
|
|
||||||
|
**Diffs alone are not enough.** Read the full file(s) being modified to understand context. Code that looks wrong in isolation may be correct given surrounding logic.
|
||||||
|
|
||||||
|
## What to Look For
|
||||||
|
|
||||||
|
**Bugs** — Primary focus.
|
||||||
|
- Logic errors, off-by-one mistakes, incorrect conditionals
|
||||||
|
- Missing guards, unreachable code paths, broken error handling
|
||||||
|
- Edge cases: null/empty inputs, race conditions
|
||||||
|
- Security: injection, auth bypass, data exposure
|
||||||
|
|
||||||
|
**Structure** — Does the code fit the codebase?
|
||||||
|
- Follows existing patterns and conventions?
|
||||||
|
- Uses established abstractions?
|
||||||
|
- Excessive nesting that could be flattened?
|
||||||
|
|
||||||
|
**Performance** — Only flag if obviously problematic.
|
||||||
|
- O(n²) on unbounded data, N+1 queries, blocking I/O on hot paths
|
||||||
|
|
||||||
|
## Before You Flag Something
|
||||||
|
|
||||||
|
- **Be certain.** Don't flag something as a bug if you're unsure — investigate first.
|
||||||
|
- **Don't invent hypothetical problems.** If an edge case matters, explain the realistic scenario.
|
||||||
|
- **Don't be a zealot about style.** Some "violations" are acceptable when they're the simplest option.
|
||||||
|
- Only review the changes — not pre-existing code that wasn't modified.
|
||||||
|
|
||||||
|
## Output
|
||||||
|
|
||||||
|
- Be direct about bugs and why they're bugs
|
||||||
|
- Communicate severity honestly — don't overstate
|
||||||
|
- Include file paths and line numbers
|
||||||
|
- Suggest fixes when appropriate
|
||||||
|
- Matter-of-fact tone, no flattery
|
||||||
11
profiles/opencode/command/code-review.md
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11
profiles/opencode/command/code-review.md
Normal file
@@ -0,0 +1,11 @@
|
|||||||
|
---
|
||||||
|
description: Review changes with parallel @code-review subagents
|
||||||
|
agent: plan
|
||||||
|
---
|
||||||
|
Review the code changes using THREE (3) @code-review subagents and correlate results into a summary ranked by severity. Use the provided user guidance to steer the review and focus on specific code paths, changes, and/or areas of concern.
|
||||||
|
|
||||||
|
Guidance: $ARGUMENTS
|
||||||
|
|
||||||
|
First, call `skill({ name: 'vcs-detect' })` to determine whether the repo uses git or jj, then use the appropriate VCS commands throughout.
|
||||||
|
|
||||||
|
Review uncommitted changes by default. If no uncommitted changes, review the last commit. If the user provides a pull request/merge request number or link, use CLI tools (gh/glab) to fetch it and then perform your review.
|
||||||
17
profiles/opencode/command/session-export.md
Normal file
17
profiles/opencode/command/session-export.md
Normal file
@@ -0,0 +1,17 @@
|
|||||||
|
---
|
||||||
|
description: Add AI session summary to GitHub PR or GitLab MR description
|
||||||
|
---
|
||||||
|
|
||||||
|
Update the PR/MR description with an AI session export summary.
|
||||||
|
|
||||||
|
First, invoke the skill tool to load the session-export skill:
|
||||||
|
|
||||||
|
```
|
||||||
|
skill({ name: 'session-export' })
|
||||||
|
```
|
||||||
|
|
||||||
|
Then follow the skill instructions to export the session summary.
|
||||||
|
|
||||||
|
<user-request>
|
||||||
|
$ARGUMENTS
|
||||||
|
</user-request>
|
||||||
41
profiles/opencode/skill/frontend-design/SKILL.md
Normal file
41
profiles/opencode/skill/frontend-design/SKILL.md
Normal file
@@ -0,0 +1,41 @@
|
|||||||
|
---
|
||||||
|
name: frontend-design
|
||||||
|
description: Create distinctive, production-grade frontend interfaces with high design quality. Use this skill when the user asks to build web components, pages, artifacts, posters, or applications (examples include websites, landing pages, dashboards, React components, HTML/CSS layouts, or when styling/beautifying any web UI). Generates creative, polished code and UI design that avoids generic AI aesthetics.
|
||||||
|
---
|
||||||
|
|
||||||
|
This skill guides creation of distinctive, production-grade frontend interfaces that avoid generic "AI slop" aesthetics. Implement real working code with exceptional attention to aesthetic details and creative choices.
|
||||||
|
|
||||||
|
The user provides frontend requirements: a component, page, application, or interface to build. They may include context about the purpose, audience, or technical constraints.
|
||||||
|
|
||||||
|
## Design Thinking
|
||||||
|
|
||||||
|
Before coding, understand the context and commit to a BOLD aesthetic direction:
|
||||||
|
- **Purpose**: What problem does this interface solve? Who uses it?
|
||||||
|
- **Tone**: Pick an extreme: brutally minimal, maximalist chaos, retro-futuristic, organic/natural, luxury/refined, playful/toy-like, editorial/magazine, brutalist/raw, art deco/geometric, soft/pastel, industrial/utilitarian, etc. There are so many flavors to choose from. Use these for inspiration but design one that is true to the aesthetic direction.
|
||||||
|
- **Constraints**: Technical requirements (framework, performance, accessibility).
|
||||||
|
- **Differentiation**: What makes this UNFORGETTABLE? What's the one thing someone will remember?
|
||||||
|
|
||||||
|
**CRITICAL**: Choose a clear conceptual direction and execute it with precision. Bold maximalism and refined minimalism both work - the key is intentionality, not intensity.
|
||||||
|
|
||||||
|
Then implement working code (HTML/CSS/JS, React, Vue, etc.) that is:
|
||||||
|
- Production-grade and functional
|
||||||
|
- Visually striking and memorable
|
||||||
|
- Cohesive with a clear aesthetic point-of-view
|
||||||
|
- Meticulously refined in every detail
|
||||||
|
|
||||||
|
## Frontend Aesthetics Guidelines
|
||||||
|
|
||||||
|
Focus on:
|
||||||
|
- **Typography**: Choose fonts that are beautiful, unique, and interesting. Avoid generic fonts like Arial and Inter; opt instead for distinctive choices that elevate the frontend's aesthetics; unexpected, characterful font choices. Pair a distinctive display font with a refined body font.
|
||||||
|
- **Color & Theme**: Commit to a cohesive aesthetic. Use CSS variables for consistency. Dominant colors with sharp accents outperform timid, evenly-distributed palettes.
|
||||||
|
- **Motion**: Use animations for effects and micro-interactions. Prioritize CSS-only solutions for HTML. Use Motion library for React when available. Focus on high-impact moments: one well-orchestrated page load with staggered reveals (animation-delay) creates more delight than scattered micro-interactions. Use scroll-triggering and hover states that surprise.
|
||||||
|
- **Spatial Composition**: Unexpected layouts. Asymmetry. Overlap. Diagonal flow. Grid-breaking elements. Generous negative space OR controlled density.
|
||||||
|
- **Backgrounds & Visual Details**: Create atmosphere and depth rather than defaulting to solid colors. Add contextual effects and textures that match the overall aesthetic. Apply creative forms like gradient meshes, noise textures, geometric patterns, layered transparencies, dramatic shadows, decorative borders, custom cursors, and grain overlays.
|
||||||
|
|
||||||
|
NEVER use generic AI-generated aesthetics like overused font families (Inter, Roboto, Arial, system fonts), cliched color schemes (particularly purple gradients on white backgrounds), predictable layouts and component patterns, and cookie-cutter design that lacks context-specific character.
|
||||||
|
|
||||||
|
Interpret creatively and make unexpected choices that feel genuinely designed for the context. No design should be the same. Vary between light and dark themes, different fonts, different aesthetics. NEVER converge on common choices (Space Grotesk, for example) across generations.
|
||||||
|
|
||||||
|
**IMPORTANT**: Match implementation complexity to the aesthetic vision. Maximalist designs need elaborate code with extensive animations and effects. Minimalist or refined designs need restraint, precision, and careful attention to spacing, typography, and subtle details. Elegance comes from executing the vision well.
|
||||||
|
|
||||||
|
Remember: Claude is capable of extraordinary creative work. Don't hold back, show what can truly be created when thinking outside the box and committing fully to a distinctive vision.
|
||||||
123
profiles/opencode/skill/librarian/SKILL.md
Normal file
123
profiles/opencode/skill/librarian/SKILL.md
Normal file
@@ -0,0 +1,123 @@
|
|||||||
|
---
|
||||||
|
name: librarian
|
||||||
|
description: Multi-repository codebase exploration. Research library internals, find code patterns, understand architecture, compare implementations across GitHub/npm/PyPI/crates. Use when needing deep understanding of how libraries work, finding implementations across open source, or exploring remote repository structure.
|
||||||
|
references:
|
||||||
|
- references/tool-routing.md
|
||||||
|
- references/opensrc-api.md
|
||||||
|
- references/opensrc-examples.md
|
||||||
|
- references/linking.md
|
||||||
|
- references/diagrams.md
|
||||||
|
---
|
||||||
|
|
||||||
|
# Librarian Skill
|
||||||
|
|
||||||
|
Deep codebase exploration across remote repositories.
|
||||||
|
|
||||||
|
## How to Use This Skill
|
||||||
|
|
||||||
|
### Reference Structure
|
||||||
|
|
||||||
|
| File | Purpose | When to Read |
|
||||||
|
|------|---------|--------------|
|
||||||
|
| `tool-routing.md` | Tool selection decision trees | **Always read first** |
|
||||||
|
| `opensrc-api.md` | API reference, types | Writing opensrc code |
|
||||||
|
| `opensrc-examples.md` | JavaScript patterns, workflows | Implementation examples |
|
||||||
|
| `linking.md` | GitHub URL patterns | Formatting responses |
|
||||||
|
| `diagrams.md` | Mermaid patterns | Visualizing architecture |
|
||||||
|
|
||||||
|
### Reading Order
|
||||||
|
|
||||||
|
1. **Start** with `tool-routing.md` → choose tool strategy
|
||||||
|
2. **If using opensrc:**
|
||||||
|
- Read `opensrc-api.md` for API details
|
||||||
|
- Read `opensrc-examples.md` for patterns
|
||||||
|
3. **Before responding:** `linking.md` + `diagrams.md` for output formatting
|
||||||
|
|
||||||
|
## Tool Arsenal
|
||||||
|
|
||||||
|
| Tool | Best For | Limitations |
|
||||||
|
|------|----------|-------------|
|
||||||
|
| **grep_app** | Find patterns across ALL public GitHub | Literal search only |
|
||||||
|
| **context7** | Library docs, API examples, usage | Known libraries only |
|
||||||
|
| **opensrc** | Fetch full source for deep exploration | Must fetch before read |
|
||||||
|
|
||||||
|
## Quick Decision Trees
|
||||||
|
|
||||||
|
### "How does X work?"
|
||||||
|
|
||||||
|
```
|
||||||
|
Known library?
|
||||||
|
├─ Yes → context7.resolve-library-id → context7.query-docs
|
||||||
|
│ └─ Need internals? → opensrc.fetch → read source
|
||||||
|
└─ No → grep_app search → opensrc.fetch top result
|
||||||
|
```
|
||||||
|
|
||||||
|
### "Find pattern X"
|
||||||
|
|
||||||
|
```
|
||||||
|
Specific repo?
|
||||||
|
├─ Yes → opensrc.fetch → opensrc.grep → read matches
|
||||||
|
└─ No → grep_app (broad) → opensrc.fetch interesting repos
|
||||||
|
```
|
||||||
|
|
||||||
|
### "Explore repo structure"
|
||||||
|
|
||||||
|
```
|
||||||
|
1. opensrc.fetch(target)
|
||||||
|
2. opensrc.tree(source.name) → quick overview
|
||||||
|
3. opensrc.files(source.name, "**/*.ts") → detailed listing
|
||||||
|
4. Read: README, package.json, src/index.*
|
||||||
|
5. Create architecture diagram (see diagrams.md)
|
||||||
|
```
|
||||||
|
|
||||||
|
### "Compare X vs Y"
|
||||||
|
|
||||||
|
```
|
||||||
|
1. opensrc.fetch(["X", "Y"])
|
||||||
|
2. Use source.name from results for subsequent calls
|
||||||
|
3. opensrc.grep(pattern, { sources: [nameX, nameY] })
|
||||||
|
4. Read comparable files, synthesize differences
|
||||||
|
```
|
||||||
|
|
||||||
|
## Critical: Source Naming Convention
|
||||||
|
|
||||||
|
**After fetching, always use `source.name` for subsequent calls:**
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
const [{ source }] = await opensrc.fetch("vercel/ai");
|
||||||
|
const files = await opensrc.files(source.name, "**/*.ts");
|
||||||
|
```
|
||||||
|
|
||||||
|
| Type | Fetch Spec | Source Name |
|
||||||
|
|------|------------|-------------|
|
||||||
|
| npm | `"zod"` | `"zod"` |
|
||||||
|
| npm scoped | `"@tanstack/react-query"` | `"@tanstack/react-query"` |
|
||||||
|
| pypi | `"pypi:requests"` | `"requests"` |
|
||||||
|
| crates | `"crates:serde"` | `"serde"` |
|
||||||
|
| GitHub | `"vercel/ai"` | `"github.com/vercel/ai"` |
|
||||||
|
| GitLab | `"gitlab:org/repo"` | `"gitlab.com/org/repo"` |
|
||||||
|
|
||||||
|
## When NOT to Use opensrc
|
||||||
|
|
||||||
|
| Scenario | Use Instead |
|
||||||
|
|----------|-------------|
|
||||||
|
| Simple library API questions | context7 |
|
||||||
|
| Finding examples across many repos | grep_app |
|
||||||
|
| Very large monorepos (>10GB) | Clone locally |
|
||||||
|
| Private repositories | Direct access |
|
||||||
|
|
||||||
|
## Output Guidelines
|
||||||
|
|
||||||
|
1. **Comprehensive final message** - only last message returns to main agent
|
||||||
|
2. **Parallel tool calls** - maximize efficiency
|
||||||
|
3. **Link every file reference** - see `linking.md`
|
||||||
|
4. **Diagram complex relationships** - see `diagrams.md`
|
||||||
|
5. **Never mention tool names** - say "I'll search" not "I'll use opensrc"
|
||||||
|
|
||||||
|
## References
|
||||||
|
|
||||||
|
- [Tool Routing Decision Trees](references/tool-routing.md)
|
||||||
|
- [opensrc API Reference](references/opensrc-api.md)
|
||||||
|
- [opensrc Code Examples](references/opensrc-examples.md)
|
||||||
|
- [GitHub Linking Patterns](references/linking.md)
|
||||||
|
- [Mermaid Diagram Patterns](references/diagrams.md)
|
||||||
51
profiles/opencode/skill/librarian/references/diagrams.md
Normal file
51
profiles/opencode/skill/librarian/references/diagrams.md
Normal file
@@ -0,0 +1,51 @@
|
|||||||
|
# Mermaid Diagram Patterns
|
||||||
|
|
||||||
|
Create diagrams for:
|
||||||
|
- Architecture (component relationships)
|
||||||
|
- Data flow (request → response)
|
||||||
|
- Dependencies (import graph)
|
||||||
|
- Sequences (step-by-step processes)
|
||||||
|
|
||||||
|
## Architecture
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
graph TD
|
||||||
|
A[Client] --> B[API Gateway]
|
||||||
|
B --> C[Auth Service]
|
||||||
|
B --> D[Data Service]
|
||||||
|
D --> E[(Database)]
|
||||||
|
```
|
||||||
|
|
||||||
|
## Flow
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
flowchart LR
|
||||||
|
Input --> Parse --> Validate --> Transform --> Output
|
||||||
|
```
|
||||||
|
|
||||||
|
## Sequence
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
sequenceDiagram
|
||||||
|
Client->>+Server: Request
|
||||||
|
Server->>+DB: Query
|
||||||
|
DB-->>-Server: Result
|
||||||
|
Server-->>-Client: Response
|
||||||
|
```
|
||||||
|
|
||||||
|
## When to Use
|
||||||
|
|
||||||
|
| Type | Use For |
|
||||||
|
|------|---------|
|
||||||
|
| `graph TD` | Component hierarchy, dependencies |
|
||||||
|
| `flowchart LR` | Data transformation, pipelines |
|
||||||
|
| `sequenceDiagram` | Request/response, multi-party interaction |
|
||||||
|
| `classDiagram` | Type relationships, inheritance |
|
||||||
|
| `stateDiagram` | State machines, lifecycle |
|
||||||
|
|
||||||
|
## Tips
|
||||||
|
|
||||||
|
- Keep nodes short (3-4 words max)
|
||||||
|
- Use subgraphs for grouping related components
|
||||||
|
- Arrow labels for relationship types
|
||||||
|
- Prefer LR (left-right) for flows, TD (top-down) for hierarchies
|
||||||
61
profiles/opencode/skill/librarian/references/linking.md
Normal file
61
profiles/opencode/skill/librarian/references/linking.md
Normal file
@@ -0,0 +1,61 @@
|
|||||||
|
# GitHub Linking Patterns
|
||||||
|
|
||||||
|
All file/dir/code refs → fluent markdown links. Never raw URLs.
|
||||||
|
|
||||||
|
## URL Formats
|
||||||
|
|
||||||
|
### File
|
||||||
|
```
|
||||||
|
https://github.com/{owner}/{repo}/blob/{ref}/{path}
|
||||||
|
```
|
||||||
|
|
||||||
|
### File + Lines
|
||||||
|
```
|
||||||
|
https://github.com/{owner}/{repo}/blob/{ref}/{path}#L{start}-L{end}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Directory
|
||||||
|
```
|
||||||
|
https://github.com/{owner}/{repo}/tree/{ref}/{path}
|
||||||
|
```
|
||||||
|
|
||||||
|
### GitLab (note `/-/blob/`)
|
||||||
|
```
|
||||||
|
https://gitlab.com/{owner}/{repo}/-/blob/{ref}/{path}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Ref Resolution
|
||||||
|
|
||||||
|
| Source | Use as ref |
|
||||||
|
|--------|------------|
|
||||||
|
| Known version | `v{version}` |
|
||||||
|
| Default branch | `main` or `master` |
|
||||||
|
| opensrc fetch | ref from result |
|
||||||
|
| Specific commit | full SHA |
|
||||||
|
|
||||||
|
## Examples
|
||||||
|
|
||||||
|
### Correct
|
||||||
|
```markdown
|
||||||
|
The [`parseAsync`](https://github.com/colinhacks/zod/blob/main/src/types.ts#L450-L480) method handles...
|
||||||
|
```
|
||||||
|
|
||||||
|
### Wrong
|
||||||
|
```markdown
|
||||||
|
See https://github.com/colinhacks/zod/blob/main/src/types.ts#L100
|
||||||
|
The parseAsync method in src/types.ts handles...
|
||||||
|
```
|
||||||
|
|
||||||
|
## Line Numbers
|
||||||
|
|
||||||
|
- Single: `#L42`
|
||||||
|
- Range: `#L42-L50`
|
||||||
|
- Prefer ranges for context (2-5 lines around key code)
|
||||||
|
|
||||||
|
## Registry → GitHub
|
||||||
|
|
||||||
|
| Registry | Find repo in |
|
||||||
|
|----------|--------------|
|
||||||
|
| npm | `package.json` → `repository` |
|
||||||
|
| PyPI | `pyproject.toml` or setup.py |
|
||||||
|
| crates | `Cargo.toml` |
|
||||||
235
profiles/opencode/skill/librarian/references/opensrc-api.md
Normal file
235
profiles/opencode/skill/librarian/references/opensrc-api.md
Normal file
@@ -0,0 +1,235 @@
|
|||||||
|
# opensrc API Reference
|
||||||
|
|
||||||
|
## Tool
|
||||||
|
|
||||||
|
Use the **opensrc MCP server** via single tool:
|
||||||
|
|
||||||
|
| Tool | Purpose |
|
||||||
|
|------|---------|
|
||||||
|
| `opensrc_execute` | All operations (fetch, read, grep, files, remove, etc.) |
|
||||||
|
|
||||||
|
Takes a `code` parameter: JavaScript async arrow function executed server-side. Source trees stay on server, only results return.
|
||||||
|
|
||||||
|
## API Surface
|
||||||
|
|
||||||
|
### Read Operations
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// List all fetched sources
|
||||||
|
opensrc.list(): Source[]
|
||||||
|
|
||||||
|
// Check if source exists
|
||||||
|
opensrc.has(name: string, version?: string): boolean
|
||||||
|
|
||||||
|
// Get source metadata
|
||||||
|
opensrc.get(name: string): Source | undefined
|
||||||
|
|
||||||
|
// List files with optional glob
|
||||||
|
opensrc.files(sourceName: string, glob?: string): Promise<FileEntry[]>
|
||||||
|
|
||||||
|
// Get directory tree structure (default depth: 3)
|
||||||
|
opensrc.tree(sourceName: string, options?: { depth?: number }): Promise<TreeNode>
|
||||||
|
|
||||||
|
// Regex search file contents
|
||||||
|
opensrc.grep(pattern: string, options?: GrepOptions): Promise<GrepResult[]>
|
||||||
|
|
||||||
|
// AST-based semantic code search
|
||||||
|
opensrc.astGrep(sourceName: string, pattern: string, options?: AstGrepOptions): Promise<AstGrepMatch[]>
|
||||||
|
|
||||||
|
// Read single file
|
||||||
|
opensrc.read(sourceName: string, filePath: string): Promise<string>
|
||||||
|
|
||||||
|
// Batch read multiple files (supports globs!)
|
||||||
|
opensrc.readMany(sourceName: string, paths: string[]): Promise<Record<string, string>>
|
||||||
|
|
||||||
|
// Parse fetch spec
|
||||||
|
opensrc.resolve(spec: string): Promise<ParsedSpec>
|
||||||
|
```
|
||||||
|
|
||||||
|
### Mutation Operations
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Fetch packages/repos
|
||||||
|
opensrc.fetch(specs: string | string[], options?: { modify?: boolean }): Promise<FetchedSource[]>
|
||||||
|
|
||||||
|
// Remove sources
|
||||||
|
opensrc.remove(names: string[]): Promise<RemoveResult>
|
||||||
|
|
||||||
|
// Clean by type
|
||||||
|
opensrc.clean(options?: CleanOptions): Promise<RemoveResult>
|
||||||
|
```
|
||||||
|
|
||||||
|
## Types
|
||||||
|
|
||||||
|
### Source
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface Source {
|
||||||
|
type: "npm" | "pypi" | "crates" | "repo";
|
||||||
|
name: string; // Use this for all subsequent calls
|
||||||
|
version?: string;
|
||||||
|
ref?: string;
|
||||||
|
path: string;
|
||||||
|
fetchedAt: string;
|
||||||
|
repository: string;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### FetchedSource
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface FetchedSource {
|
||||||
|
source: Source; // IMPORTANT: use source.name for subsequent calls
|
||||||
|
alreadyExists: boolean;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### GrepOptions
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface GrepOptions {
|
||||||
|
sources?: string[]; // Filter to specific sources
|
||||||
|
include?: string; // File glob pattern (e.g., "*.ts")
|
||||||
|
maxResults?: number; // Limit results (default: 100)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### GrepResult
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface GrepResult {
|
||||||
|
source: string;
|
||||||
|
file: string;
|
||||||
|
line: number;
|
||||||
|
content: string;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### AstGrepOptions
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface AstGrepOptions {
|
||||||
|
glob?: string; // File glob pattern (e.g., "**/*.ts")
|
||||||
|
lang?: string | string[]; // Language(s): "js", "ts", "tsx", "html", "css"
|
||||||
|
limit?: number; // Max results (default: 1000)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### AstGrepMatch
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface AstGrepMatch {
|
||||||
|
file: string;
|
||||||
|
line: number;
|
||||||
|
column: number;
|
||||||
|
endLine: number;
|
||||||
|
endColumn: number;
|
||||||
|
text: string; // Matched code text
|
||||||
|
metavars: Record<string, string>; // Captured $VAR → text
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
#### AST Pattern Syntax
|
||||||
|
|
||||||
|
| Pattern | Matches |
|
||||||
|
|---------|---------|
|
||||||
|
| `$NAME` | Single node, captures to metavars |
|
||||||
|
| `$$$ARGS` | Zero or more nodes (variadic), captures |
|
||||||
|
| `$_` | Single node, no capture |
|
||||||
|
| `$$$` | Zero or more nodes, no capture |
|
||||||
|
|
||||||
|
### FileEntry
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface FileEntry {
|
||||||
|
path: string;
|
||||||
|
size: number;
|
||||||
|
isDirectory: boolean;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### TreeNode
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface TreeNode {
|
||||||
|
name: string;
|
||||||
|
type: "file" | "dir";
|
||||||
|
children?: TreeNode[]; // only for dirs
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### CleanOptions
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface CleanOptions {
|
||||||
|
packages?: boolean;
|
||||||
|
repos?: boolean;
|
||||||
|
npm?: boolean;
|
||||||
|
pypi?: boolean;
|
||||||
|
crates?: boolean;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### RemoveResult
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface RemoveResult {
|
||||||
|
success: boolean;
|
||||||
|
removed: string[];
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Error Handling
|
||||||
|
|
||||||
|
Operations throw on errors. Wrap in try/catch if needed:
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
try {
|
||||||
|
const content = await opensrc.read("zod", "missing.ts");
|
||||||
|
return content;
|
||||||
|
} catch (e) {
|
||||||
|
return { error: e.message };
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
`readMany` returns errors as string values prefixed with `[Error:`:
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
const files = await opensrc.readMany("zod", ["exists.ts", "missing.ts"]);
|
||||||
|
// { "exists.ts": "content...", "missing.ts": "[Error: ENOENT...]" }
|
||||||
|
|
||||||
|
// Filter successful reads
|
||||||
|
const successful = Object.entries(files)
|
||||||
|
.filter(([_, content]) => !content.startsWith("[Error:"));
|
||||||
|
```
|
||||||
|
|
||||||
|
## Package Spec Formats
|
||||||
|
|
||||||
|
| Format | Example | Source Name After Fetch |
|
||||||
|
|--------|---------|------------------------|
|
||||||
|
| `<name>` | `"zod"` | `"zod"` |
|
||||||
|
| `<name>@<version>` | `"zod@3.22.0"` | `"zod"` |
|
||||||
|
| `pypi:<name>` | `"pypi:requests"` | `"requests"` |
|
||||||
|
| `crates:<name>` | `"crates:serde"` | `"serde"` |
|
||||||
|
| `owner/repo` | `"vercel/ai"` | `"github.com/vercel/ai"` |
|
||||||
|
| `owner/repo@ref` | `"vercel/ai@v1.0.0"` | `"github.com/vercel/ai"` |
|
||||||
|
| `gitlab:owner/repo` | `"gitlab:org/repo"` | `"gitlab.com/org/repo"` |
|
||||||
|
|
||||||
|
## Critical Pattern
|
||||||
|
|
||||||
|
**Always capture `source.name` from fetch results:**
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("vercel/ai");
|
||||||
|
|
||||||
|
// GitHub repos: "vercel/ai" → "github.com/vercel/ai"
|
||||||
|
const sourceName = source.name;
|
||||||
|
|
||||||
|
// Use sourceName for ALL subsequent calls
|
||||||
|
const files = await opensrc.files(sourceName, "src/**/*.ts");
|
||||||
|
return files;
|
||||||
|
}
|
||||||
|
```
|
||||||
336
profiles/opencode/skill/librarian/references/opensrc-examples.md
Normal file
336
profiles/opencode/skill/librarian/references/opensrc-examples.md
Normal file
@@ -0,0 +1,336 @@
|
|||||||
|
# opensrc Code Examples
|
||||||
|
|
||||||
|
## Workflow: Fetch → Explore
|
||||||
|
|
||||||
|
### Basic Fetch and Explore with tree()
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("vercel/ai");
|
||||||
|
// Get directory structure first
|
||||||
|
const tree = await opensrc.tree(source.name, { depth: 2 });
|
||||||
|
return tree;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Fetch and Read Key Files
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("vercel/ai");
|
||||||
|
const sourceName = source.name; // "github.com/vercel/ai"
|
||||||
|
|
||||||
|
const files = await opensrc.readMany(sourceName, [
|
||||||
|
"package.json",
|
||||||
|
"README.md",
|
||||||
|
"src/index.ts"
|
||||||
|
]);
|
||||||
|
|
||||||
|
return { sourceName, files };
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### readMany with Globs
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("zod");
|
||||||
|
// Read all package.json files in monorepo
|
||||||
|
const files = await opensrc.readMany(source.name, [
|
||||||
|
"packages/*/package.json" // globs supported!
|
||||||
|
]);
|
||||||
|
return Object.keys(files);
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Batch Fetch Multiple Packages
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const results = await opensrc.fetch(["zod", "valibot", "yup"]);
|
||||||
|
const names = results.map(r => r.source.name);
|
||||||
|
|
||||||
|
// Compare how each handles string validation
|
||||||
|
const comparisons = {};
|
||||||
|
for (const name of names) {
|
||||||
|
const matches = await opensrc.grep("string.*validate|validateString", {
|
||||||
|
sources: [name],
|
||||||
|
include: "*.ts",
|
||||||
|
maxResults: 10
|
||||||
|
});
|
||||||
|
comparisons[name] = matches.map(m => `${m.file}:${m.line}`);
|
||||||
|
}
|
||||||
|
return comparisons;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Search Patterns
|
||||||
|
|
||||||
|
### Grep → Read Context
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const matches = await opensrc.grep("export function parse\\(", {
|
||||||
|
sources: ["zod"],
|
||||||
|
include: "*.ts"
|
||||||
|
});
|
||||||
|
|
||||||
|
if (matches.length === 0) return "No matches";
|
||||||
|
|
||||||
|
const match = matches[0];
|
||||||
|
const content = await opensrc.read(match.source, match.file);
|
||||||
|
const lines = content.split("\n");
|
||||||
|
|
||||||
|
// Return 40 lines starting from match
|
||||||
|
return {
|
||||||
|
file: match.file,
|
||||||
|
code: lines.slice(match.line - 1, match.line + 39).join("\n")
|
||||||
|
};
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Search Across All Fetched Sources
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const sources = opensrc.list();
|
||||||
|
const results = {};
|
||||||
|
|
||||||
|
for (const source of sources) {
|
||||||
|
const errorHandling = await opensrc.grep("throw new|catch \\(|\\.catch\\(", {
|
||||||
|
sources: [source.name],
|
||||||
|
include: "*.ts",
|
||||||
|
maxResults: 20
|
||||||
|
});
|
||||||
|
results[source.name] = {
|
||||||
|
type: source.type,
|
||||||
|
errorPatterns: errorHandling.length
|
||||||
|
};
|
||||||
|
}
|
||||||
|
|
||||||
|
return results;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## AST-Based Search
|
||||||
|
|
||||||
|
Use `astGrep` for semantic code search with pattern matching.
|
||||||
|
|
||||||
|
### Find Function Declarations
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("lodash");
|
||||||
|
|
||||||
|
const fns = await opensrc.astGrep(source.name, "function $NAME($$$ARGS) { $$$BODY }", {
|
||||||
|
lang: "js",
|
||||||
|
limit: 20
|
||||||
|
});
|
||||||
|
|
||||||
|
return fns.map(m => ({
|
||||||
|
file: m.file,
|
||||||
|
line: m.line,
|
||||||
|
name: m.metavars.NAME
|
||||||
|
}));
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Find React Hooks Usage
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("vercel/ai");
|
||||||
|
|
||||||
|
const stateHooks = await opensrc.astGrep(
|
||||||
|
source.name,
|
||||||
|
"const [$STATE, $SETTER] = useState($$$INIT)",
|
||||||
|
{ lang: ["ts", "tsx"], limit: 50 }
|
||||||
|
);
|
||||||
|
|
||||||
|
return stateHooks.map(m => ({
|
||||||
|
file: m.file,
|
||||||
|
state: m.metavars.STATE,
|
||||||
|
setter: m.metavars.SETTER
|
||||||
|
}));
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Find Class Definitions with Context
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const [{ source }] = await opensrc.fetch("zod");
|
||||||
|
|
||||||
|
const classes = await opensrc.astGrep(source.name, "class $NAME", {
|
||||||
|
glob: "**/*.ts"
|
||||||
|
});
|
||||||
|
|
||||||
|
const details = [];
|
||||||
|
for (const cls of classes.slice(0, 5)) {
|
||||||
|
const content = await opensrc.read(source.name, cls.file);
|
||||||
|
const lines = content.split("\n");
|
||||||
|
details.push({
|
||||||
|
name: cls.metavars.NAME,
|
||||||
|
file: cls.file,
|
||||||
|
preview: lines.slice(cls.line - 1, cls.line + 9).join("\n")
|
||||||
|
});
|
||||||
|
}
|
||||||
|
return details;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Compare Export Patterns Across Libraries
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const results = await opensrc.fetch(["zod", "valibot"]);
|
||||||
|
const names = results.map(r => r.source.name);
|
||||||
|
|
||||||
|
const exports = {};
|
||||||
|
for (const name of names) {
|
||||||
|
const matches = await opensrc.astGrep(name, "export const $NAME = $_", {
|
||||||
|
lang: "ts",
|
||||||
|
limit: 30
|
||||||
|
});
|
||||||
|
exports[name] = matches.map(m => m.metavars.NAME);
|
||||||
|
}
|
||||||
|
return exports;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### grep vs astGrep
|
||||||
|
|
||||||
|
| Use Case | Tool |
|
||||||
|
|----------|------|
|
||||||
|
| Text/regex pattern | `grep` |
|
||||||
|
| Function declarations | `astGrep`: `function $NAME($$$) { $$$ }` |
|
||||||
|
| Arrow functions | `astGrep`: `const $N = ($$$) => $_` |
|
||||||
|
| Class definitions | `astGrep`: `class $NAME extends $PARENT` |
|
||||||
|
| Import statements | `astGrep`: `import { $$$IMPORTS } from "$MOD"` |
|
||||||
|
| JSX components | `astGrep`: `<$COMP $$$PROPS />` |
|
||||||
|
|
||||||
|
## Repository Exploration
|
||||||
|
|
||||||
|
### Find Entry Points
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const name = "github.com/vercel/ai";
|
||||||
|
|
||||||
|
const allFiles = await opensrc.files(name, "**/*.{ts,js}");
|
||||||
|
const entryPoints = allFiles.filter(f =>
|
||||||
|
f.path.match(/^(src\/)?(index|main|mod)\.(ts|js)$/) ||
|
||||||
|
f.path.includes("/index.ts")
|
||||||
|
);
|
||||||
|
|
||||||
|
// Read all entry points
|
||||||
|
const contents = {};
|
||||||
|
for (const ep of entryPoints.slice(0, 5)) {
|
||||||
|
contents[ep.path] = await opensrc.read(name, ep.path);
|
||||||
|
}
|
||||||
|
|
||||||
|
return {
|
||||||
|
totalFiles: allFiles.length,
|
||||||
|
entryPoints: entryPoints.map(f => f.path),
|
||||||
|
contents
|
||||||
|
};
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Explore Package Structure
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const name = "zod";
|
||||||
|
|
||||||
|
// Get all TypeScript files
|
||||||
|
const tsFiles = await opensrc.files(name, "**/*.ts");
|
||||||
|
|
||||||
|
// Group by directory
|
||||||
|
const byDir = {};
|
||||||
|
for (const f of tsFiles) {
|
||||||
|
const dir = f.path.split("/").slice(0, -1).join("/") || ".";
|
||||||
|
byDir[dir] = (byDir[dir] || 0) + 1;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Read key files
|
||||||
|
const pkg = await opensrc.read(name, "package.json");
|
||||||
|
const readme = await opensrc.read(name, "README.md");
|
||||||
|
|
||||||
|
return {
|
||||||
|
structure: byDir,
|
||||||
|
package: JSON.parse(pkg),
|
||||||
|
readmePreview: readme.slice(0, 500)
|
||||||
|
};
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Batch Operations
|
||||||
|
|
||||||
|
### Read Many with Error Handling
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const files = await opensrc.readMany("zod", [
|
||||||
|
"src/index.ts",
|
||||||
|
"src/types.ts",
|
||||||
|
"src/ZodError.ts",
|
||||||
|
"src/helpers/parseUtil.ts"
|
||||||
|
]);
|
||||||
|
|
||||||
|
// files is Record<string, string> - errors start with "[Error:"
|
||||||
|
const successful = Object.entries(files)
|
||||||
|
.filter(([_, content]) => !content.startsWith("[Error:"))
|
||||||
|
.map(([path, content]) => ({ path, lines: content.split("\n").length }));
|
||||||
|
|
||||||
|
return successful;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
### Parallel Grep Across Multiple Sources
|
||||||
|
|
||||||
|
```javascript
|
||||||
|
async () => {
|
||||||
|
const targets = ["zod", "valibot"];
|
||||||
|
const pattern = "export (type|interface)";
|
||||||
|
|
||||||
|
const results = await Promise.all(
|
||||||
|
targets.map(async (name) => {
|
||||||
|
const matches = await opensrc.grep(pattern, {
|
||||||
|
sources: [name],
|
||||||
|
include: "*.ts",
|
||||||
|
maxResults: 50
|
||||||
|
});
|
||||||
|
return { name, count: matches.length, matches };
|
||||||
|
})
|
||||||
|
);
|
||||||
|
|
||||||
|
return results;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Workflow Checklist
|
||||||
|
|
||||||
|
### Comprehensive Repository Analysis
|
||||||
|
|
||||||
|
```
|
||||||
|
Repository Analysis Progress:
|
||||||
|
- [ ] 1. Fetch repository
|
||||||
|
- [ ] 2. Read package.json + README
|
||||||
|
- [ ] 3. Identify entry points (src/index.*)
|
||||||
|
- [ ] 4. Read main entry file
|
||||||
|
- [ ] 5. Map exports and public API
|
||||||
|
- [ ] 6. Trace key functionality
|
||||||
|
- [ ] 7. Create architecture diagram
|
||||||
|
```
|
||||||
|
|
||||||
|
### Library Comparison
|
||||||
|
|
||||||
|
```
|
||||||
|
Comparison Progress:
|
||||||
|
- [ ] 1. Fetch all libraries
|
||||||
|
- [ ] 2. Grep for target pattern in each
|
||||||
|
- [ ] 3. Read matching implementations
|
||||||
|
- [ ] 4. Create comparison table
|
||||||
|
- [ ] 5. Synthesize findings
|
||||||
|
```
|
||||||
109
profiles/opencode/skill/librarian/references/tool-routing.md
Normal file
109
profiles/opencode/skill/librarian/references/tool-routing.md
Normal file
@@ -0,0 +1,109 @@
|
|||||||
|
# Tool Routing
|
||||||
|
|
||||||
|
## Decision Flowchart
|
||||||
|
|
||||||
|
```mermaid
|
||||||
|
graph TD
|
||||||
|
Q[User Query] --> T{Query Type?}
|
||||||
|
T -->|Understand/Explain| U[UNDERSTAND]
|
||||||
|
T -->|Find/Search| F[FIND]
|
||||||
|
T -->|Explore/Architecture| E[EXPLORE]
|
||||||
|
T -->|Compare| C[COMPARE]
|
||||||
|
|
||||||
|
U --> U1{Known library?}
|
||||||
|
U1 -->|Yes| U2[context7.resolve-library-id]
|
||||||
|
U2 --> U3[context7.query-docs]
|
||||||
|
U3 --> U4{Need source?}
|
||||||
|
U4 -->|Yes| U5[opensrc.fetch → read]
|
||||||
|
U1 -->|No| U6[grep_app → opensrc.fetch]
|
||||||
|
|
||||||
|
F --> F1{Specific repo?}
|
||||||
|
F1 -->|Yes| F2[opensrc.fetch → grep → read]
|
||||||
|
F1 -->|No| F3[grep_app broad search]
|
||||||
|
F3 --> F4[opensrc.fetch interesting repos]
|
||||||
|
|
||||||
|
E --> E1[opensrc.fetch]
|
||||||
|
E1 --> E2[opensrc.files]
|
||||||
|
E2 --> E3[Read entry points]
|
||||||
|
E3 --> E4[Create diagram]
|
||||||
|
|
||||||
|
C --> C1["opensrc.fetch([X, Y])"]
|
||||||
|
C1 --> C2[grep same pattern]
|
||||||
|
C2 --> C3[Read comparable files]
|
||||||
|
C3 --> C4[Synthesize comparison]
|
||||||
|
```
|
||||||
|
|
||||||
|
## Query Type Detection
|
||||||
|
|
||||||
|
| Keywords | Query Type | Start With |
|
||||||
|
|----------|------------|------------|
|
||||||
|
| "how does", "why does", "explain", "purpose of" | UNDERSTAND | context7 |
|
||||||
|
| "find", "where is", "implementations of", "examples of" | FIND | grep_app |
|
||||||
|
| "explore", "walk through", "architecture", "structure" | EXPLORE | opensrc |
|
||||||
|
| "compare", "vs", "difference between" | COMPARE | opensrc |
|
||||||
|
|
||||||
|
## UNDERSTAND Queries
|
||||||
|
|
||||||
|
```
|
||||||
|
Known library? → context7.resolve-library-id → context7.query-docs
|
||||||
|
└─ Need source? → opensrc.fetch → read
|
||||||
|
|
||||||
|
Unknown? → grep_app search → opensrc.fetch top result → read
|
||||||
|
```
|
||||||
|
|
||||||
|
**When to transition context7 → opensrc:**
|
||||||
|
- Need implementation details (not just API docs)
|
||||||
|
- Question about internals/private methods
|
||||||
|
- Tracing code flow through library
|
||||||
|
|
||||||
|
## FIND Queries
|
||||||
|
|
||||||
|
```
|
||||||
|
Specific repo? → opensrc.fetch → opensrc.grep → read matches
|
||||||
|
|
||||||
|
Broad search? → grep_app → analyze → opensrc.fetch interesting repos
|
||||||
|
```
|
||||||
|
|
||||||
|
**grep_app query tips:**
|
||||||
|
- Use literal code patterns: `useState(` not "react hooks"
|
||||||
|
- Filter by language: `language: ["TypeScript"]`
|
||||||
|
- Narrow by repo: `repo: "vercel/"` for org
|
||||||
|
|
||||||
|
## EXPLORE Queries
|
||||||
|
|
||||||
|
```
|
||||||
|
1. opensrc.fetch(target)
|
||||||
|
2. opensrc.files → understand structure
|
||||||
|
3. Identify entry points: README, package.json, src/index.*
|
||||||
|
4. Read entry → internals
|
||||||
|
5. Create architecture diagram
|
||||||
|
```
|
||||||
|
|
||||||
|
## COMPARE Queries
|
||||||
|
|
||||||
|
```
|
||||||
|
1. opensrc.fetch([X, Y])
|
||||||
|
2. Extract source.name from each result
|
||||||
|
3. opensrc.grep same pattern in both
|
||||||
|
4. Read comparable files
|
||||||
|
5. Synthesize → comparison table
|
||||||
|
```
|
||||||
|
|
||||||
|
## Tool Capabilities
|
||||||
|
|
||||||
|
| Tool | Best For | Not For |
|
||||||
|
|------|----------|---------|
|
||||||
|
| **grep_app** | Broad search, unknown scope, finding repos | Semantic queries |
|
||||||
|
| **context7** | Library APIs, best practices, common patterns | Library internals |
|
||||||
|
| **opensrc** | Deep exploration, reading internals, tracing flow | Initial discovery |
|
||||||
|
|
||||||
|
## Anti-patterns
|
||||||
|
|
||||||
|
| Don't | Do |
|
||||||
|
|-------|-----|
|
||||||
|
| grep_app for known library docs | context7 first |
|
||||||
|
| opensrc.fetch before knowing target | grep_app to discover |
|
||||||
|
| Multiple small reads | opensrc.readMany batch |
|
||||||
|
| Describe without linking | Link every file ref |
|
||||||
|
| Text for complex relationships | Mermaid diagram |
|
||||||
|
| Use tool names in responses | "I'll search..." not "I'll use opensrc" |
|
||||||
122
profiles/opencode/skill/session-export/SKILL.md
Normal file
122
profiles/opencode/skill/session-export/SKILL.md
Normal file
@@ -0,0 +1,122 @@
|
|||||||
|
---
|
||||||
|
name: session-export
|
||||||
|
description: Update GitHub PR descriptions with AI session export summaries. Use when user asks to add session summary to PR/MR, document AI assistance in PR/MR, or export conversation summary to PR/MR description.
|
||||||
|
---
|
||||||
|
|
||||||
|
# Session Export
|
||||||
|
|
||||||
|
Update PR/MR descriptions with a structured summary of the AI-assisted conversation.
|
||||||
|
|
||||||
|
## Output Format
|
||||||
|
|
||||||
|
```markdown
|
||||||
|
> [!NOTE]
|
||||||
|
> This PR was written with AI assistance.
|
||||||
|
|
||||||
|
<details><summary>AI Session Export</summary>
|
||||||
|
<p>
|
||||||
|
|
||||||
|
```json
|
||||||
|
{
|
||||||
|
"info": {
|
||||||
|
"title": "<brief task description>",
|
||||||
|
"agent": "opencode",
|
||||||
|
"models": ["<model(s) used>"]
|
||||||
|
},
|
||||||
|
"summary": [
|
||||||
|
"<action 1>",
|
||||||
|
"<action 2>",
|
||||||
|
...
|
||||||
|
]
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
</p>
|
||||||
|
</details>
|
||||||
|
```
|
||||||
|
|
||||||
|
## Workflow
|
||||||
|
|
||||||
|
### 1. Export Session Data
|
||||||
|
|
||||||
|
Get session data using OpenCode CLI:
|
||||||
|
|
||||||
|
```bash
|
||||||
|
opencode export [sessionID]
|
||||||
|
```
|
||||||
|
|
||||||
|
Returns JSON with session info including models used. Use current session if no sessionID provided.
|
||||||
|
|
||||||
|
### 2. Generate Summary JSON
|
||||||
|
|
||||||
|
From exported data and conversation context, create summary:
|
||||||
|
|
||||||
|
- **title**: 2-5 word task description (lowercase)
|
||||||
|
- **agent**: always "opencode"
|
||||||
|
- **models**: array from export data
|
||||||
|
- **summary**: array of terse action statements
|
||||||
|
- Use past tense ("added", "fixed", "created")
|
||||||
|
- Start with "user requested..." or "user asked..."
|
||||||
|
- Chronological order
|
||||||
|
- Attempt to keep the summary to a max of 25 turns ("user requested", "agent did")
|
||||||
|
- **NEVER include sensitive data**: API keys, credentials, secrets, tokens, passwords, env vars
|
||||||
|
|
||||||
|
### 3. Update PR/MR Description
|
||||||
|
|
||||||
|
**GitHub:**
|
||||||
|
```bash
|
||||||
|
gh pr edit <PR_NUMBER> --body "$(cat <<'EOF'
|
||||||
|
<existing description>
|
||||||
|
|
||||||
|
> [!NOTE]
|
||||||
|
> This PR was written with AI assistance.
|
||||||
|
|
||||||
|
<details><summary>AI Session Export</summary>
|
||||||
|
...
|
||||||
|
</details>
|
||||||
|
EOF
|
||||||
|
)"
|
||||||
|
```
|
||||||
|
|
||||||
|
### 4. Preserve Existing Content
|
||||||
|
|
||||||
|
Always fetch and preserve existing PR/MR description:
|
||||||
|
|
||||||
|
```bash
|
||||||
|
# GitHub
|
||||||
|
gh pr view <PR_NUMBER> --json body -q '.body'
|
||||||
|
|
||||||
|
Append session export after existing content with blank line separator.
|
||||||
|
|
||||||
|
## Example Summary
|
||||||
|
|
||||||
|
For a session where user asked to add dark mode:
|
||||||
|
|
||||||
|
```json
|
||||||
|
{
|
||||||
|
"info": {
|
||||||
|
"title": "dark mode implementation",
|
||||||
|
"agent": "opencode",
|
||||||
|
"models": ["claude sonnet 4"]
|
||||||
|
},
|
||||||
|
"summary": [
|
||||||
|
"user requested dark mode toggle in settings",
|
||||||
|
"agent explored existing theme system",
|
||||||
|
"agent created ThemeContext for state management",
|
||||||
|
"agent added DarkModeToggle component",
|
||||||
|
"agent updated CSS variables for dark theme",
|
||||||
|
"agent ran tests and fixed 2 failures",
|
||||||
|
"agent committed changes"
|
||||||
|
]
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Security
|
||||||
|
|
||||||
|
**NEVER include in summary:**
|
||||||
|
- API keys, tokens, secrets
|
||||||
|
- Passwords, credentials
|
||||||
|
- Environment variable values
|
||||||
|
- Private URLs with auth tokens
|
||||||
|
- Personal identifiable information
|
||||||
|
- Internal hostnames/IPs
|
||||||
70
profiles/opencode/skill/vcs-detect/SKILL.md
Normal file
70
profiles/opencode/skill/vcs-detect/SKILL.md
Normal file
@@ -0,0 +1,70 @@
|
|||||||
|
---
|
||||||
|
name: vcs-detect
|
||||||
|
description: Detect whether the current project uses jj (Jujutsu) or git for version control. Run this BEFORE any VCS command to use the correct tool.
|
||||||
|
---
|
||||||
|
|
||||||
|
# VCS Detection Skill
|
||||||
|
|
||||||
|
Detect the version control system in use before running any VCS commands.
|
||||||
|
|
||||||
|
## Why This Matters
|
||||||
|
|
||||||
|
- jj (Jujutsu) and git have different CLIs and workflows
|
||||||
|
- Running `git` commands in a jj repo (or vice versa) causes errors
|
||||||
|
- Some repos use jj with git colocated (both `.jj/` and `.git/` exist)
|
||||||
|
|
||||||
|
## Detection Logic
|
||||||
|
|
||||||
|
Both `jj root` and `git rev-parse --show-toplevel` walk up the filesystem to find repo root.
|
||||||
|
|
||||||
|
**Priority order:**
|
||||||
|
|
||||||
|
1. `jj root` succeeds → jj (handles colocated too)
|
||||||
|
2. `git rev-parse` succeeds → git
|
||||||
|
3. Both fail → no VCS
|
||||||
|
|
||||||
|
## Detection Command
|
||||||
|
|
||||||
|
```bash
|
||||||
|
if jj root &>/dev/null; then echo "jj"
|
||||||
|
elif git rev-parse --show-toplevel &>/dev/null; then echo "git"
|
||||||
|
else echo "none"
|
||||||
|
fi
|
||||||
|
```
|
||||||
|
|
||||||
|
## Command Mappings
|
||||||
|
|
||||||
|
| Operation | git | jj |
|
||||||
|
|-----------|-----|-----|
|
||||||
|
| Status | `git status` | `jj status` |
|
||||||
|
| Log | `git log` | `jj log` |
|
||||||
|
| Diff | `git diff` | `jj diff` |
|
||||||
|
| Commit | `git commit` | `jj commit` / `jj describe` |
|
||||||
|
| Branch list | `git branch` | `jj branch list` |
|
||||||
|
| New branch | `git checkout -b <name>` | `jj branch create <name>` |
|
||||||
|
| Push | `git push` | `jj git push` |
|
||||||
|
| Pull/Fetch | `git pull` / `git fetch` | `jj git fetch` |
|
||||||
|
| Rebase | `git rebase` | `jj rebase` |
|
||||||
|
|
||||||
|
## Usage
|
||||||
|
|
||||||
|
Before any VCS operation:
|
||||||
|
|
||||||
|
1. Run detection command
|
||||||
|
2. Use appropriate CLI based on result
|
||||||
|
3. If `none`, warn user directory is not version controlled
|
||||||
|
|
||||||
|
## Example Integration
|
||||||
|
|
||||||
|
```
|
||||||
|
User: Show me the git log
|
||||||
|
Agent: [Runs detection] -> Result: jj
|
||||||
|
Agent: [Runs `jj log` instead of `git log`]
|
||||||
|
```
|
||||||
|
|
||||||
|
## Colocated Repos
|
||||||
|
|
||||||
|
When both `.jj/` and `.git/` exist, the repo is "colocated":
|
||||||
|
- jj manages the working copy
|
||||||
|
- git is available for compatibility (GitHub, etc.)
|
||||||
|
- **Always prefer jj commands** in colocated repos
|
||||||
2934
profiles/opencode/skill/vercel-react-best-practices/AGENTS.md
Normal file
2934
profiles/opencode/skill/vercel-react-best-practices/AGENTS.md
Normal file
File diff suppressed because it is too large
Load Diff
136
profiles/opencode/skill/vercel-react-best-practices/SKILL.md
Normal file
136
profiles/opencode/skill/vercel-react-best-practices/SKILL.md
Normal file
@@ -0,0 +1,136 @@
|
|||||||
|
---
|
||||||
|
name: vercel-react-best-practices
|
||||||
|
description: React and Next.js performance optimization guidelines from Vercel Engineering. This skill should be used when writing, reviewing, or refactoring React/Next.js code to ensure optimal performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements.
|
||||||
|
license: MIT
|
||||||
|
metadata:
|
||||||
|
author: vercel
|
||||||
|
version: "1.0.0"
|
||||||
|
---
|
||||||
|
|
||||||
|
# Vercel React Best Practices
|
||||||
|
|
||||||
|
Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 57 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.
|
||||||
|
|
||||||
|
## When to Apply
|
||||||
|
|
||||||
|
Reference these guidelines when:
|
||||||
|
- Writing new React components or Next.js pages
|
||||||
|
- Implementing data fetching (client or server-side)
|
||||||
|
- Reviewing code for performance issues
|
||||||
|
- Refactoring existing React/Next.js code
|
||||||
|
- Optimizing bundle size or load times
|
||||||
|
|
||||||
|
## Rule Categories by Priority
|
||||||
|
|
||||||
|
| Priority | Category | Impact | Prefix |
|
||||||
|
|----------|----------|--------|--------|
|
||||||
|
| 1 | Eliminating Waterfalls | CRITICAL | `async-` |
|
||||||
|
| 2 | Bundle Size Optimization | CRITICAL | `bundle-` |
|
||||||
|
| 3 | Server-Side Performance | HIGH | `server-` |
|
||||||
|
| 4 | Client-Side Data Fetching | MEDIUM-HIGH | `client-` |
|
||||||
|
| 5 | Re-render Optimization | MEDIUM | `rerender-` |
|
||||||
|
| 6 | Rendering Performance | MEDIUM | `rendering-` |
|
||||||
|
| 7 | JavaScript Performance | LOW-MEDIUM | `js-` |
|
||||||
|
| 8 | Advanced Patterns | LOW | `advanced-` |
|
||||||
|
|
||||||
|
## Quick Reference
|
||||||
|
|
||||||
|
### 1. Eliminating Waterfalls (CRITICAL)
|
||||||
|
|
||||||
|
- `async-defer-await` - Move await into branches where actually used
|
||||||
|
- `async-parallel` - Use Promise.all() for independent operations
|
||||||
|
- `async-dependencies` - Use better-all for partial dependencies
|
||||||
|
- `async-api-routes` - Start promises early, await late in API routes
|
||||||
|
- `async-suspense-boundaries` - Use Suspense to stream content
|
||||||
|
|
||||||
|
### 2. Bundle Size Optimization (CRITICAL)
|
||||||
|
|
||||||
|
- `bundle-barrel-imports` - Import directly, avoid barrel files
|
||||||
|
- `bundle-dynamic-imports` - Use next/dynamic for heavy components
|
||||||
|
- `bundle-defer-third-party` - Load analytics/logging after hydration
|
||||||
|
- `bundle-conditional` - Load modules only when feature is activated
|
||||||
|
- `bundle-preload` - Preload on hover/focus for perceived speed
|
||||||
|
|
||||||
|
### 3. Server-Side Performance (HIGH)
|
||||||
|
|
||||||
|
- `server-auth-actions` - Authenticate server actions like API routes
|
||||||
|
- `server-cache-react` - Use React.cache() for per-request deduplication
|
||||||
|
- `server-cache-lru` - Use LRU cache for cross-request caching
|
||||||
|
- `server-dedup-props` - Avoid duplicate serialization in RSC props
|
||||||
|
- `server-serialization` - Minimize data passed to client components
|
||||||
|
- `server-parallel-fetching` - Restructure components to parallelize fetches
|
||||||
|
- `server-after-nonblocking` - Use after() for non-blocking operations
|
||||||
|
|
||||||
|
### 4. Client-Side Data Fetching (MEDIUM-HIGH)
|
||||||
|
|
||||||
|
- `client-swr-dedup` - Use SWR for automatic request deduplication
|
||||||
|
- `client-event-listeners` - Deduplicate global event listeners
|
||||||
|
- `client-passive-event-listeners` - Use passive listeners for scroll
|
||||||
|
- `client-localstorage-schema` - Version and minimize localStorage data
|
||||||
|
|
||||||
|
### 5. Re-render Optimization (MEDIUM)
|
||||||
|
|
||||||
|
- `rerender-defer-reads` - Don't subscribe to state only used in callbacks
|
||||||
|
- `rerender-memo` - Extract expensive work into memoized components
|
||||||
|
- `rerender-memo-with-default-value` - Hoist default non-primitive props
|
||||||
|
- `rerender-dependencies` - Use primitive dependencies in effects
|
||||||
|
- `rerender-derived-state` - Subscribe to derived booleans, not raw values
|
||||||
|
- `rerender-derived-state-no-effect` - Derive state during render, not effects
|
||||||
|
- `rerender-functional-setstate` - Use functional setState for stable callbacks
|
||||||
|
- `rerender-lazy-state-init` - Pass function to useState for expensive values
|
||||||
|
- `rerender-simple-expression-in-memo` - Avoid memo for simple primitives
|
||||||
|
- `rerender-move-effect-to-event` - Put interaction logic in event handlers
|
||||||
|
- `rerender-transitions` - Use startTransition for non-urgent updates
|
||||||
|
- `rerender-use-ref-transient-values` - Use refs for transient frequent values
|
||||||
|
|
||||||
|
### 6. Rendering Performance (MEDIUM)
|
||||||
|
|
||||||
|
- `rendering-animate-svg-wrapper` - Animate div wrapper, not SVG element
|
||||||
|
- `rendering-content-visibility` - Use content-visibility for long lists
|
||||||
|
- `rendering-hoist-jsx` - Extract static JSX outside components
|
||||||
|
- `rendering-svg-precision` - Reduce SVG coordinate precision
|
||||||
|
- `rendering-hydration-no-flicker` - Use inline script for client-only data
|
||||||
|
- `rendering-hydration-suppress-warning` - Suppress expected mismatches
|
||||||
|
- `rendering-activity` - Use Activity component for show/hide
|
||||||
|
- `rendering-conditional-render` - Use ternary, not && for conditionals
|
||||||
|
- `rendering-usetransition-loading` - Prefer useTransition for loading state
|
||||||
|
|
||||||
|
### 7. JavaScript Performance (LOW-MEDIUM)
|
||||||
|
|
||||||
|
- `js-batch-dom-css` - Group CSS changes via classes or cssText
|
||||||
|
- `js-index-maps` - Build Map for repeated lookups
|
||||||
|
- `js-cache-property-access` - Cache object properties in loops
|
||||||
|
- `js-cache-function-results` - Cache function results in module-level Map
|
||||||
|
- `js-cache-storage` - Cache localStorage/sessionStorage reads
|
||||||
|
- `js-combine-iterations` - Combine multiple filter/map into one loop
|
||||||
|
- `js-length-check-first` - Check array length before expensive comparison
|
||||||
|
- `js-early-exit` - Return early from functions
|
||||||
|
- `js-hoist-regexp` - Hoist RegExp creation outside loops
|
||||||
|
- `js-min-max-loop` - Use loop for min/max instead of sort
|
||||||
|
- `js-set-map-lookups` - Use Set/Map for O(1) lookups
|
||||||
|
- `js-tosorted-immutable` - Use toSorted() for immutability
|
||||||
|
|
||||||
|
### 8. Advanced Patterns (LOW)
|
||||||
|
|
||||||
|
- `advanced-event-handler-refs` - Store event handlers in refs
|
||||||
|
- `advanced-init-once` - Initialize app once per app load
|
||||||
|
- `advanced-use-latest` - useLatest for stable callback refs
|
||||||
|
|
||||||
|
## How to Use
|
||||||
|
|
||||||
|
Read individual rule files for detailed explanations and code examples:
|
||||||
|
|
||||||
|
```
|
||||||
|
rules/async-parallel.md
|
||||||
|
rules/bundle-barrel-imports.md
|
||||||
|
```
|
||||||
|
|
||||||
|
Each rule file contains:
|
||||||
|
- Brief explanation of why it matters
|
||||||
|
- Incorrect code example with explanation
|
||||||
|
- Correct code example with explanation
|
||||||
|
- Additional context and references
|
||||||
|
|
||||||
|
## Full Compiled Document
|
||||||
|
|
||||||
|
For the complete guide with all rules expanded: `AGENTS.md`
|
||||||
@@ -0,0 +1,46 @@
|
|||||||
|
# Sections
|
||||||
|
|
||||||
|
This file defines all sections, their ordering, impact levels, and descriptions.
|
||||||
|
The section ID (in parentheses) is the filename prefix used to group rules.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 1. Eliminating Waterfalls (async)
|
||||||
|
|
||||||
|
**Impact:** CRITICAL
|
||||||
|
**Description:** Waterfalls are the #1 performance killer. Each sequential await adds full network latency. Eliminating them yields the largest gains.
|
||||||
|
|
||||||
|
## 2. Bundle Size Optimization (bundle)
|
||||||
|
|
||||||
|
**Impact:** CRITICAL
|
||||||
|
**Description:** Reducing initial bundle size improves Time to Interactive and Largest Contentful Paint.
|
||||||
|
|
||||||
|
## 3. Server-Side Performance (server)
|
||||||
|
|
||||||
|
**Impact:** HIGH
|
||||||
|
**Description:** Optimizing server-side rendering and data fetching eliminates server-side waterfalls and reduces response times.
|
||||||
|
|
||||||
|
## 4. Client-Side Data Fetching (client)
|
||||||
|
|
||||||
|
**Impact:** MEDIUM-HIGH
|
||||||
|
**Description:** Automatic deduplication and efficient data fetching patterns reduce redundant network requests.
|
||||||
|
|
||||||
|
## 5. Re-render Optimization (rerender)
|
||||||
|
|
||||||
|
**Impact:** MEDIUM
|
||||||
|
**Description:** Reducing unnecessary re-renders minimizes wasted computation and improves UI responsiveness.
|
||||||
|
|
||||||
|
## 6. Rendering Performance (rendering)
|
||||||
|
|
||||||
|
**Impact:** MEDIUM
|
||||||
|
**Description:** Optimizing the rendering process reduces the work the browser needs to do.
|
||||||
|
|
||||||
|
## 7. JavaScript Performance (js)
|
||||||
|
|
||||||
|
**Impact:** LOW-MEDIUM
|
||||||
|
**Description:** Micro-optimizations for hot paths can add up to meaningful improvements.
|
||||||
|
|
||||||
|
## 8. Advanced Patterns (advanced)
|
||||||
|
|
||||||
|
**Impact:** LOW
|
||||||
|
**Description:** Advanced patterns for specific cases that require careful implementation.
|
||||||
@@ -0,0 +1,28 @@
|
|||||||
|
---
|
||||||
|
title: Rule Title Here
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: Optional description of impact (e.g., "20-50% improvement")
|
||||||
|
tags: tag1, tag2
|
||||||
|
---
|
||||||
|
|
||||||
|
## Rule Title Here
|
||||||
|
|
||||||
|
**Impact: MEDIUM (optional impact description)**
|
||||||
|
|
||||||
|
Brief explanation of the rule and why it matters. This should be clear and concise, explaining the performance implications.
|
||||||
|
|
||||||
|
**Incorrect (description of what's wrong):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Bad code example here
|
||||||
|
const bad = example()
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (description of what's right):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Good code example here
|
||||||
|
const good = example()
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [Link to documentation or resource](https://example.com)
|
||||||
@@ -0,0 +1,55 @@
|
|||||||
|
---
|
||||||
|
title: Store Event Handlers in Refs
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: stable subscriptions
|
||||||
|
tags: advanced, hooks, refs, event-handlers, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Store Event Handlers in Refs
|
||||||
|
|
||||||
|
Store callbacks in refs when used in effects that shouldn't re-subscribe on callback changes.
|
||||||
|
|
||||||
|
**Incorrect (re-subscribes on every render):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function useWindowEvent(event: string, handler: (e) => void) {
|
||||||
|
useEffect(() => {
|
||||||
|
window.addEventListener(event, handler)
|
||||||
|
return () => window.removeEventListener(event, handler)
|
||||||
|
}, [event, handler])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (stable subscription):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function useWindowEvent(event: string, handler: (e) => void) {
|
||||||
|
const handlerRef = useRef(handler)
|
||||||
|
useEffect(() => {
|
||||||
|
handlerRef.current = handler
|
||||||
|
}, [handler])
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
const listener = (e) => handlerRef.current(e)
|
||||||
|
window.addEventListener(event, listener)
|
||||||
|
return () => window.removeEventListener(event, listener)
|
||||||
|
}, [event])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Alternative: use `useEffectEvent` if you're on latest React:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { useEffectEvent } from 'react'
|
||||||
|
|
||||||
|
function useWindowEvent(event: string, handler: (e) => void) {
|
||||||
|
const onEvent = useEffectEvent(handler)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
window.addEventListener(event, onEvent)
|
||||||
|
return () => window.removeEventListener(event, onEvent)
|
||||||
|
}, [event])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
`useEffectEvent` provides a cleaner API for the same pattern: it creates a stable function reference that always calls the latest version of the handler.
|
||||||
@@ -0,0 +1,42 @@
|
|||||||
|
---
|
||||||
|
title: Initialize App Once, Not Per Mount
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: avoids duplicate init in development
|
||||||
|
tags: initialization, useEffect, app-startup, side-effects
|
||||||
|
---
|
||||||
|
|
||||||
|
## Initialize App Once, Not Per Mount
|
||||||
|
|
||||||
|
Do not put app-wide initialization that must run once per app load inside `useEffect([])` of a component. Components can remount and effects will re-run. Use a module-level guard or top-level init in the entry module instead.
|
||||||
|
|
||||||
|
**Incorrect (runs twice in dev, re-runs on remount):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Comp() {
|
||||||
|
useEffect(() => {
|
||||||
|
loadFromStorage()
|
||||||
|
checkAuthToken()
|
||||||
|
}, [])
|
||||||
|
|
||||||
|
// ...
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (once per app load):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
let didInit = false
|
||||||
|
|
||||||
|
function Comp() {
|
||||||
|
useEffect(() => {
|
||||||
|
if (didInit) return
|
||||||
|
didInit = true
|
||||||
|
loadFromStorage()
|
||||||
|
checkAuthToken()
|
||||||
|
}, [])
|
||||||
|
|
||||||
|
// ...
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [Initializing the application](https://react.dev/learn/you-might-not-need-an-effect#initializing-the-application)
|
||||||
@@ -0,0 +1,39 @@
|
|||||||
|
---
|
||||||
|
title: useEffectEvent for Stable Callback Refs
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: prevents effect re-runs
|
||||||
|
tags: advanced, hooks, useEffectEvent, refs, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## useEffectEvent for Stable Callback Refs
|
||||||
|
|
||||||
|
Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.
|
||||||
|
|
||||||
|
**Incorrect (effect re-runs on every callback change):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
const timeout = setTimeout(() => onSearch(query), 300)
|
||||||
|
return () => clearTimeout(timeout)
|
||||||
|
}, [query, onSearch])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (using React's useEffectEvent):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { useEffectEvent } from 'react';
|
||||||
|
|
||||||
|
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
const onSearchEvent = useEffectEvent(onSearch)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
const timeout = setTimeout(() => onSearchEvent(query), 300)
|
||||||
|
return () => clearTimeout(timeout)
|
||||||
|
}, [query])
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,38 @@
|
|||||||
|
---
|
||||||
|
title: Prevent Waterfall Chains in API Routes
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: 2-10× improvement
|
||||||
|
tags: api-routes, server-actions, waterfalls, parallelization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Prevent Waterfall Chains in API Routes
|
||||||
|
|
||||||
|
In API routes and Server Actions, start independent operations immediately, even if you don't await them yet.
|
||||||
|
|
||||||
|
**Incorrect (config waits for auth, data waits for both):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
export async function GET(request: Request) {
|
||||||
|
const session = await auth()
|
||||||
|
const config = await fetchConfig()
|
||||||
|
const data = await fetchData(session.user.id)
|
||||||
|
return Response.json({ data, config })
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (auth and config start immediately):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
export async function GET(request: Request) {
|
||||||
|
const sessionPromise = auth()
|
||||||
|
const configPromise = fetchConfig()
|
||||||
|
const session = await sessionPromise
|
||||||
|
const [config, data] = await Promise.all([
|
||||||
|
configPromise,
|
||||||
|
fetchData(session.user.id)
|
||||||
|
])
|
||||||
|
return Response.json({ data, config })
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
For operations with more complex dependency chains, use `better-all` to automatically maximize parallelism (see Dependency-Based Parallelization).
|
||||||
@@ -0,0 +1,80 @@
|
|||||||
|
---
|
||||||
|
title: Defer Await Until Needed
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: avoids blocking unused code paths
|
||||||
|
tags: async, await, conditional, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Defer Await Until Needed
|
||||||
|
|
||||||
|
Move `await` operations into the branches where they're actually used to avoid blocking code paths that don't need them.
|
||||||
|
|
||||||
|
**Incorrect (blocks both branches):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
async function handleRequest(userId: string, skipProcessing: boolean) {
|
||||||
|
const userData = await fetchUserData(userId)
|
||||||
|
|
||||||
|
if (skipProcessing) {
|
||||||
|
// Returns immediately but still waited for userData
|
||||||
|
return { skipped: true }
|
||||||
|
}
|
||||||
|
|
||||||
|
// Only this branch uses userData
|
||||||
|
return processUserData(userData)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (only blocks when needed):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
async function handleRequest(userId: string, skipProcessing: boolean) {
|
||||||
|
if (skipProcessing) {
|
||||||
|
// Returns immediately without waiting
|
||||||
|
return { skipped: true }
|
||||||
|
}
|
||||||
|
|
||||||
|
// Fetch only when needed
|
||||||
|
const userData = await fetchUserData(userId)
|
||||||
|
return processUserData(userData)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Another example (early return optimization):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Incorrect: always fetches permissions
|
||||||
|
async function updateResource(resourceId: string, userId: string) {
|
||||||
|
const permissions = await fetchPermissions(userId)
|
||||||
|
const resource = await getResource(resourceId)
|
||||||
|
|
||||||
|
if (!resource) {
|
||||||
|
return { error: 'Not found' }
|
||||||
|
}
|
||||||
|
|
||||||
|
if (!permissions.canEdit) {
|
||||||
|
return { error: 'Forbidden' }
|
||||||
|
}
|
||||||
|
|
||||||
|
return await updateResourceData(resource, permissions)
|
||||||
|
}
|
||||||
|
|
||||||
|
// Correct: fetches only when needed
|
||||||
|
async function updateResource(resourceId: string, userId: string) {
|
||||||
|
const resource = await getResource(resourceId)
|
||||||
|
|
||||||
|
if (!resource) {
|
||||||
|
return { error: 'Not found' }
|
||||||
|
}
|
||||||
|
|
||||||
|
const permissions = await fetchPermissions(userId)
|
||||||
|
|
||||||
|
if (!permissions.canEdit) {
|
||||||
|
return { error: 'Forbidden' }
|
||||||
|
}
|
||||||
|
|
||||||
|
return await updateResourceData(resource, permissions)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
This optimization is especially valuable when the skipped branch is frequently taken, or when the deferred operation is expensive.
|
||||||
@@ -0,0 +1,51 @@
|
|||||||
|
---
|
||||||
|
title: Dependency-Based Parallelization
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: 2-10× improvement
|
||||||
|
tags: async, parallelization, dependencies, better-all
|
||||||
|
---
|
||||||
|
|
||||||
|
## Dependency-Based Parallelization
|
||||||
|
|
||||||
|
For operations with partial dependencies, use `better-all` to maximize parallelism. It automatically starts each task at the earliest possible moment.
|
||||||
|
|
||||||
|
**Incorrect (profile waits for config unnecessarily):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const [user, config] = await Promise.all([
|
||||||
|
fetchUser(),
|
||||||
|
fetchConfig()
|
||||||
|
])
|
||||||
|
const profile = await fetchProfile(user.id)
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (config and profile run in parallel):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
import { all } from 'better-all'
|
||||||
|
|
||||||
|
const { user, config, profile } = await all({
|
||||||
|
async user() { return fetchUser() },
|
||||||
|
async config() { return fetchConfig() },
|
||||||
|
async profile() {
|
||||||
|
return fetchProfile((await this.$.user).id)
|
||||||
|
}
|
||||||
|
})
|
||||||
|
```
|
||||||
|
|
||||||
|
**Alternative without extra dependencies:**
|
||||||
|
|
||||||
|
We can also create all the promises first, and do `Promise.all()` at the end.
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const userPromise = fetchUser()
|
||||||
|
const profilePromise = userPromise.then(user => fetchProfile(user.id))
|
||||||
|
|
||||||
|
const [user, config, profile] = await Promise.all([
|
||||||
|
userPromise,
|
||||||
|
fetchConfig(),
|
||||||
|
profilePromise
|
||||||
|
])
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [https://github.com/shuding/better-all](https://github.com/shuding/better-all)
|
||||||
@@ -0,0 +1,28 @@
|
|||||||
|
---
|
||||||
|
title: Promise.all() for Independent Operations
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: 2-10× improvement
|
||||||
|
tags: async, parallelization, promises, waterfalls
|
||||||
|
---
|
||||||
|
|
||||||
|
## Promise.all() for Independent Operations
|
||||||
|
|
||||||
|
When async operations have no interdependencies, execute them concurrently using `Promise.all()`.
|
||||||
|
|
||||||
|
**Incorrect (sequential execution, 3 round trips):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const user = await fetchUser()
|
||||||
|
const posts = await fetchPosts()
|
||||||
|
const comments = await fetchComments()
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (parallel execution, 1 round trip):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const [user, posts, comments] = await Promise.all([
|
||||||
|
fetchUser(),
|
||||||
|
fetchPosts(),
|
||||||
|
fetchComments()
|
||||||
|
])
|
||||||
|
```
|
||||||
@@ -0,0 +1,99 @@
|
|||||||
|
---
|
||||||
|
title: Strategic Suspense Boundaries
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: faster initial paint
|
||||||
|
tags: async, suspense, streaming, layout-shift
|
||||||
|
---
|
||||||
|
|
||||||
|
## Strategic Suspense Boundaries
|
||||||
|
|
||||||
|
Instead of awaiting data in async components before returning JSX, use Suspense boundaries to show the wrapper UI faster while data loads.
|
||||||
|
|
||||||
|
**Incorrect (wrapper blocked by data fetching):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
async function Page() {
|
||||||
|
const data = await fetchData() // Blocks entire page
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<div>Sidebar</div>
|
||||||
|
<div>Header</div>
|
||||||
|
<div>
|
||||||
|
<DataDisplay data={data} />
|
||||||
|
</div>
|
||||||
|
<div>Footer</div>
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The entire layout waits for data even though only the middle section needs it.
|
||||||
|
|
||||||
|
**Correct (wrapper shows immediately, data streams in):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Page() {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<div>Sidebar</div>
|
||||||
|
<div>Header</div>
|
||||||
|
<div>
|
||||||
|
<Suspense fallback={<Skeleton />}>
|
||||||
|
<DataDisplay />
|
||||||
|
</Suspense>
|
||||||
|
</div>
|
||||||
|
<div>Footer</div>
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
async function DataDisplay() {
|
||||||
|
const data = await fetchData() // Only blocks this component
|
||||||
|
return <div>{data.content}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Sidebar, Header, and Footer render immediately. Only DataDisplay waits for data.
|
||||||
|
|
||||||
|
**Alternative (share promise across components):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Page() {
|
||||||
|
// Start fetch immediately, but don't await
|
||||||
|
const dataPromise = fetchData()
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<div>Sidebar</div>
|
||||||
|
<div>Header</div>
|
||||||
|
<Suspense fallback={<Skeleton />}>
|
||||||
|
<DataDisplay dataPromise={dataPromise} />
|
||||||
|
<DataSummary dataPromise={dataPromise} />
|
||||||
|
</Suspense>
|
||||||
|
<div>Footer</div>
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
function DataDisplay({ dataPromise }: { dataPromise: Promise<Data> }) {
|
||||||
|
const data = use(dataPromise) // Unwraps the promise
|
||||||
|
return <div>{data.content}</div>
|
||||||
|
}
|
||||||
|
|
||||||
|
function DataSummary({ dataPromise }: { dataPromise: Promise<Data> }) {
|
||||||
|
const data = use(dataPromise) // Reuses the same promise
|
||||||
|
return <div>{data.summary}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Both components share the same promise, so only one fetch occurs. Layout renders immediately while both components wait together.
|
||||||
|
|
||||||
|
**When NOT to use this pattern:**
|
||||||
|
|
||||||
|
- Critical data needed for layout decisions (affects positioning)
|
||||||
|
- SEO-critical content above the fold
|
||||||
|
- Small, fast queries where suspense overhead isn't worth it
|
||||||
|
- When you want to avoid layout shift (loading → content jump)
|
||||||
|
|
||||||
|
**Trade-off:** Faster initial paint vs potential layout shift. Choose based on your UX priorities.
|
||||||
@@ -0,0 +1,59 @@
|
|||||||
|
---
|
||||||
|
title: Avoid Barrel File Imports
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: 200-800ms import cost, slow builds
|
||||||
|
tags: bundle, imports, tree-shaking, barrel-files, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Avoid Barrel File Imports
|
||||||
|
|
||||||
|
Import directly from source files instead of barrel files to avoid loading thousands of unused modules. **Barrel files** are entry points that re-export multiple modules (e.g., `index.js` that does `export * from './module'`).
|
||||||
|
|
||||||
|
Popular icon and component libraries can have **up to 10,000 re-exports** in their entry file. For many React packages, **it takes 200-800ms just to import them**, affecting both development speed and production cold starts.
|
||||||
|
|
||||||
|
**Why tree-shaking doesn't help:** When a library is marked as external (not bundled), the bundler can't optimize it. If you bundle it to enable tree-shaking, builds become substantially slower analyzing the entire module graph.
|
||||||
|
|
||||||
|
**Incorrect (imports entire library):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { Check, X, Menu } from 'lucide-react'
|
||||||
|
// Loads 1,583 modules, takes ~2.8s extra in dev
|
||||||
|
// Runtime cost: 200-800ms on every cold start
|
||||||
|
|
||||||
|
import { Button, TextField } from '@mui/material'
|
||||||
|
// Loads 2,225 modules, takes ~4.2s extra in dev
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (imports only what you need):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import Check from 'lucide-react/dist/esm/icons/check'
|
||||||
|
import X from 'lucide-react/dist/esm/icons/x'
|
||||||
|
import Menu from 'lucide-react/dist/esm/icons/menu'
|
||||||
|
// Loads only 3 modules (~2KB vs ~1MB)
|
||||||
|
|
||||||
|
import Button from '@mui/material/Button'
|
||||||
|
import TextField from '@mui/material/TextField'
|
||||||
|
// Loads only what you use
|
||||||
|
```
|
||||||
|
|
||||||
|
**Alternative (Next.js 13.5+):**
|
||||||
|
|
||||||
|
```js
|
||||||
|
// next.config.js - use optimizePackageImports
|
||||||
|
module.exports = {
|
||||||
|
experimental: {
|
||||||
|
optimizePackageImports: ['lucide-react', '@mui/material']
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Then you can keep the ergonomic barrel imports:
|
||||||
|
import { Check, X, Menu } from 'lucide-react'
|
||||||
|
// Automatically transformed to direct imports at build time
|
||||||
|
```
|
||||||
|
|
||||||
|
Direct imports provide 15-70% faster dev boot, 28% faster builds, 40% faster cold starts, and significantly faster HMR.
|
||||||
|
|
||||||
|
Libraries commonly affected: `lucide-react`, `@mui/material`, `@mui/icons-material`, `@tabler/icons-react`, `react-icons`, `@headlessui/react`, `@radix-ui/react-*`, `lodash`, `ramda`, `date-fns`, `rxjs`, `react-use`.
|
||||||
|
|
||||||
|
Reference: [How we optimized package imports in Next.js](https://vercel.com/blog/how-we-optimized-package-imports-in-next-js)
|
||||||
@@ -0,0 +1,31 @@
|
|||||||
|
---
|
||||||
|
title: Conditional Module Loading
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: loads large data only when needed
|
||||||
|
tags: bundle, conditional-loading, lazy-loading
|
||||||
|
---
|
||||||
|
|
||||||
|
## Conditional Module Loading
|
||||||
|
|
||||||
|
Load large data or modules only when a feature is activated.
|
||||||
|
|
||||||
|
**Example (lazy-load animation frames):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function AnimationPlayer({ enabled, setEnabled }: { enabled: boolean; setEnabled: React.Dispatch<React.SetStateAction<boolean>> }) {
|
||||||
|
const [frames, setFrames] = useState<Frame[] | null>(null)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
if (enabled && !frames && typeof window !== 'undefined') {
|
||||||
|
import('./animation-frames.js')
|
||||||
|
.then(mod => setFrames(mod.frames))
|
||||||
|
.catch(() => setEnabled(false))
|
||||||
|
}
|
||||||
|
}, [enabled, frames, setEnabled])
|
||||||
|
|
||||||
|
if (!frames) return <Skeleton />
|
||||||
|
return <Canvas frames={frames} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The `typeof window !== 'undefined'` check prevents bundling this module for SSR, optimizing server bundle size and build speed.
|
||||||
@@ -0,0 +1,49 @@
|
|||||||
|
---
|
||||||
|
title: Defer Non-Critical Third-Party Libraries
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: loads after hydration
|
||||||
|
tags: bundle, third-party, analytics, defer
|
||||||
|
---
|
||||||
|
|
||||||
|
## Defer Non-Critical Third-Party Libraries
|
||||||
|
|
||||||
|
Analytics, logging, and error tracking don't block user interaction. Load them after hydration.
|
||||||
|
|
||||||
|
**Incorrect (blocks initial bundle):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { Analytics } from '@vercel/analytics/react'
|
||||||
|
|
||||||
|
export default function RootLayout({ children }) {
|
||||||
|
return (
|
||||||
|
<html>
|
||||||
|
<body>
|
||||||
|
{children}
|
||||||
|
<Analytics />
|
||||||
|
</body>
|
||||||
|
</html>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (loads after hydration):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import dynamic from 'next/dynamic'
|
||||||
|
|
||||||
|
const Analytics = dynamic(
|
||||||
|
() => import('@vercel/analytics/react').then(m => m.Analytics),
|
||||||
|
{ ssr: false }
|
||||||
|
)
|
||||||
|
|
||||||
|
export default function RootLayout({ children }) {
|
||||||
|
return (
|
||||||
|
<html>
|
||||||
|
<body>
|
||||||
|
{children}
|
||||||
|
<Analytics />
|
||||||
|
</body>
|
||||||
|
</html>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,35 @@
|
|||||||
|
---
|
||||||
|
title: Dynamic Imports for Heavy Components
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: directly affects TTI and LCP
|
||||||
|
tags: bundle, dynamic-import, code-splitting, next-dynamic
|
||||||
|
---
|
||||||
|
|
||||||
|
## Dynamic Imports for Heavy Components
|
||||||
|
|
||||||
|
Use `next/dynamic` to lazy-load large components not needed on initial render.
|
||||||
|
|
||||||
|
**Incorrect (Monaco bundles with main chunk ~300KB):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { MonacoEditor } from './monaco-editor'
|
||||||
|
|
||||||
|
function CodePanel({ code }: { code: string }) {
|
||||||
|
return <MonacoEditor value={code} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (Monaco loads on demand):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import dynamic from 'next/dynamic'
|
||||||
|
|
||||||
|
const MonacoEditor = dynamic(
|
||||||
|
() => import('./monaco-editor').then(m => m.MonacoEditor),
|
||||||
|
{ ssr: false }
|
||||||
|
)
|
||||||
|
|
||||||
|
function CodePanel({ code }: { code: string }) {
|
||||||
|
return <MonacoEditor value={code} />
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,50 @@
|
|||||||
|
---
|
||||||
|
title: Preload Based on User Intent
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: reduces perceived latency
|
||||||
|
tags: bundle, preload, user-intent, hover
|
||||||
|
---
|
||||||
|
|
||||||
|
## Preload Based on User Intent
|
||||||
|
|
||||||
|
Preload heavy bundles before they're needed to reduce perceived latency.
|
||||||
|
|
||||||
|
**Example (preload on hover/focus):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function EditorButton({ onClick }: { onClick: () => void }) {
|
||||||
|
const preload = () => {
|
||||||
|
if (typeof window !== 'undefined') {
|
||||||
|
void import('./monaco-editor')
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return (
|
||||||
|
<button
|
||||||
|
onMouseEnter={preload}
|
||||||
|
onFocus={preload}
|
||||||
|
onClick={onClick}
|
||||||
|
>
|
||||||
|
Open Editor
|
||||||
|
</button>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Example (preload when feature flag is enabled):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function FlagsProvider({ children, flags }: Props) {
|
||||||
|
useEffect(() => {
|
||||||
|
if (flags.editorEnabled && typeof window !== 'undefined') {
|
||||||
|
void import('./monaco-editor').then(mod => mod.init())
|
||||||
|
}
|
||||||
|
}, [flags.editorEnabled])
|
||||||
|
|
||||||
|
return <FlagsContext.Provider value={flags}>
|
||||||
|
{children}
|
||||||
|
</FlagsContext.Provider>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The `typeof window !== 'undefined'` check prevents bundling preloaded modules for SSR, optimizing server bundle size and build speed.
|
||||||
@@ -0,0 +1,74 @@
|
|||||||
|
---
|
||||||
|
title: Deduplicate Global Event Listeners
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: single listener for N components
|
||||||
|
tags: client, swr, event-listeners, subscription
|
||||||
|
---
|
||||||
|
|
||||||
|
## Deduplicate Global Event Listeners
|
||||||
|
|
||||||
|
Use `useSWRSubscription()` to share global event listeners across component instances.
|
||||||
|
|
||||||
|
**Incorrect (N instances = N listeners):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function useKeyboardShortcut(key: string, callback: () => void) {
|
||||||
|
useEffect(() => {
|
||||||
|
const handler = (e: KeyboardEvent) => {
|
||||||
|
if (e.metaKey && e.key === key) {
|
||||||
|
callback()
|
||||||
|
}
|
||||||
|
}
|
||||||
|
window.addEventListener('keydown', handler)
|
||||||
|
return () => window.removeEventListener('keydown', handler)
|
||||||
|
}, [key, callback])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
When using the `useKeyboardShortcut` hook multiple times, each instance will register a new listener.
|
||||||
|
|
||||||
|
**Correct (N instances = 1 listener):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import useSWRSubscription from 'swr/subscription'
|
||||||
|
|
||||||
|
// Module-level Map to track callbacks per key
|
||||||
|
const keyCallbacks = new Map<string, Set<() => void>>()
|
||||||
|
|
||||||
|
function useKeyboardShortcut(key: string, callback: () => void) {
|
||||||
|
// Register this callback in the Map
|
||||||
|
useEffect(() => {
|
||||||
|
if (!keyCallbacks.has(key)) {
|
||||||
|
keyCallbacks.set(key, new Set())
|
||||||
|
}
|
||||||
|
keyCallbacks.get(key)!.add(callback)
|
||||||
|
|
||||||
|
return () => {
|
||||||
|
const set = keyCallbacks.get(key)
|
||||||
|
if (set) {
|
||||||
|
set.delete(callback)
|
||||||
|
if (set.size === 0) {
|
||||||
|
keyCallbacks.delete(key)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}, [key, callback])
|
||||||
|
|
||||||
|
useSWRSubscription('global-keydown', () => {
|
||||||
|
const handler = (e: KeyboardEvent) => {
|
||||||
|
if (e.metaKey && keyCallbacks.has(e.key)) {
|
||||||
|
keyCallbacks.get(e.key)!.forEach(cb => cb())
|
||||||
|
}
|
||||||
|
}
|
||||||
|
window.addEventListener('keydown', handler)
|
||||||
|
return () => window.removeEventListener('keydown', handler)
|
||||||
|
})
|
||||||
|
}
|
||||||
|
|
||||||
|
function Profile() {
|
||||||
|
// Multiple shortcuts will share the same listener
|
||||||
|
useKeyboardShortcut('p', () => { /* ... */ })
|
||||||
|
useKeyboardShortcut('k', () => { /* ... */ })
|
||||||
|
// ...
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,71 @@
|
|||||||
|
---
|
||||||
|
title: Version and Minimize localStorage Data
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: prevents schema conflicts, reduces storage size
|
||||||
|
tags: client, localStorage, storage, versioning, data-minimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Version and Minimize localStorage Data
|
||||||
|
|
||||||
|
Add version prefix to keys and store only needed fields. Prevents schema conflicts and accidental storage of sensitive data.
|
||||||
|
|
||||||
|
**Incorrect:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// No version, stores everything, no error handling
|
||||||
|
localStorage.setItem('userConfig', JSON.stringify(fullUserObject))
|
||||||
|
const data = localStorage.getItem('userConfig')
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const VERSION = 'v2'
|
||||||
|
|
||||||
|
function saveConfig(config: { theme: string; language: string }) {
|
||||||
|
try {
|
||||||
|
localStorage.setItem(`userConfig:${VERSION}`, JSON.stringify(config))
|
||||||
|
} catch {
|
||||||
|
// Throws in incognito/private browsing, quota exceeded, or disabled
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
function loadConfig() {
|
||||||
|
try {
|
||||||
|
const data = localStorage.getItem(`userConfig:${VERSION}`)
|
||||||
|
return data ? JSON.parse(data) : null
|
||||||
|
} catch {
|
||||||
|
return null
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Migration from v1 to v2
|
||||||
|
function migrate() {
|
||||||
|
try {
|
||||||
|
const v1 = localStorage.getItem('userConfig:v1')
|
||||||
|
if (v1) {
|
||||||
|
const old = JSON.parse(v1)
|
||||||
|
saveConfig({ theme: old.darkMode ? 'dark' : 'light', language: old.lang })
|
||||||
|
localStorage.removeItem('userConfig:v1')
|
||||||
|
}
|
||||||
|
} catch {}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Store minimal fields from server responses:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// User object has 20+ fields, only store what UI needs
|
||||||
|
function cachePrefs(user: FullUser) {
|
||||||
|
try {
|
||||||
|
localStorage.setItem('prefs:v1', JSON.stringify({
|
||||||
|
theme: user.preferences.theme,
|
||||||
|
notifications: user.preferences.notifications
|
||||||
|
}))
|
||||||
|
} catch {}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Always wrap in try-catch:** `getItem()` and `setItem()` throw in incognito/private browsing (Safari, Firefox), when quota exceeded, or when disabled.
|
||||||
|
|
||||||
|
**Benefits:** Schema evolution via versioning, reduced storage size, prevents storing tokens/PII/internal flags.
|
||||||
@@ -0,0 +1,48 @@
|
|||||||
|
---
|
||||||
|
title: Use Passive Event Listeners for Scrolling Performance
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: eliminates scroll delay caused by event listeners
|
||||||
|
tags: client, event-listeners, scrolling, performance, touch, wheel
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Passive Event Listeners for Scrolling Performance
|
||||||
|
|
||||||
|
Add `{ passive: true }` to touch and wheel event listeners to enable immediate scrolling. Browsers normally wait for listeners to finish to check if `preventDefault()` is called, causing scroll delay.
|
||||||
|
|
||||||
|
**Incorrect:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
useEffect(() => {
|
||||||
|
const handleTouch = (e: TouchEvent) => console.log(e.touches[0].clientX)
|
||||||
|
const handleWheel = (e: WheelEvent) => console.log(e.deltaY)
|
||||||
|
|
||||||
|
document.addEventListener('touchstart', handleTouch)
|
||||||
|
document.addEventListener('wheel', handleWheel)
|
||||||
|
|
||||||
|
return () => {
|
||||||
|
document.removeEventListener('touchstart', handleTouch)
|
||||||
|
document.removeEventListener('wheel', handleWheel)
|
||||||
|
}
|
||||||
|
}, [])
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
useEffect(() => {
|
||||||
|
const handleTouch = (e: TouchEvent) => console.log(e.touches[0].clientX)
|
||||||
|
const handleWheel = (e: WheelEvent) => console.log(e.deltaY)
|
||||||
|
|
||||||
|
document.addEventListener('touchstart', handleTouch, { passive: true })
|
||||||
|
document.addEventListener('wheel', handleWheel, { passive: true })
|
||||||
|
|
||||||
|
return () => {
|
||||||
|
document.removeEventListener('touchstart', handleTouch)
|
||||||
|
document.removeEventListener('wheel', handleWheel)
|
||||||
|
}
|
||||||
|
}, [])
|
||||||
|
```
|
||||||
|
|
||||||
|
**Use passive when:** tracking/analytics, logging, any listener that doesn't call `preventDefault()`.
|
||||||
|
|
||||||
|
**Don't use passive when:** implementing custom swipe gestures, custom zoom controls, or any listener that needs `preventDefault()`.
|
||||||
@@ -0,0 +1,56 @@
|
|||||||
|
---
|
||||||
|
title: Use SWR for Automatic Deduplication
|
||||||
|
impact: MEDIUM-HIGH
|
||||||
|
impactDescription: automatic deduplication
|
||||||
|
tags: client, swr, deduplication, data-fetching
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use SWR for Automatic Deduplication
|
||||||
|
|
||||||
|
SWR enables request deduplication, caching, and revalidation across component instances.
|
||||||
|
|
||||||
|
**Incorrect (no deduplication, each instance fetches):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function UserList() {
|
||||||
|
const [users, setUsers] = useState([])
|
||||||
|
useEffect(() => {
|
||||||
|
fetch('/api/users')
|
||||||
|
.then(r => r.json())
|
||||||
|
.then(setUsers)
|
||||||
|
}, [])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (multiple instances share one request):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import useSWR from 'swr'
|
||||||
|
|
||||||
|
function UserList() {
|
||||||
|
const { data: users } = useSWR('/api/users', fetcher)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**For immutable data:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { useImmutableSWR } from '@/lib/swr'
|
||||||
|
|
||||||
|
function StaticContent() {
|
||||||
|
const { data } = useImmutableSWR('/api/config', fetcher)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**For mutations:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { useSWRMutation } from 'swr/mutation'
|
||||||
|
|
||||||
|
function UpdateButton() {
|
||||||
|
const { trigger } = useSWRMutation('/api/user', updateUser)
|
||||||
|
return <button onClick={() => trigger()}>Update</button>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [https://swr.vercel.app](https://swr.vercel.app)
|
||||||
@@ -0,0 +1,107 @@
|
|||||||
|
---
|
||||||
|
title: Avoid Layout Thrashing
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: prevents forced synchronous layouts and reduces performance bottlenecks
|
||||||
|
tags: javascript, dom, css, performance, reflow, layout-thrashing
|
||||||
|
---
|
||||||
|
|
||||||
|
## Avoid Layout Thrashing
|
||||||
|
|
||||||
|
Avoid interleaving style writes with layout reads. When you read a layout property (like `offsetWidth`, `getBoundingClientRect()`, or `getComputedStyle()`) between style changes, the browser is forced to trigger a synchronous reflow.
|
||||||
|
|
||||||
|
**This is OK (browser batches style changes):**
|
||||||
|
```typescript
|
||||||
|
function updateElementStyles(element: HTMLElement) {
|
||||||
|
// Each line invalidates style, but browser batches the recalculation
|
||||||
|
element.style.width = '100px'
|
||||||
|
element.style.height = '200px'
|
||||||
|
element.style.backgroundColor = 'blue'
|
||||||
|
element.style.border = '1px solid black'
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Incorrect (interleaved reads and writes force reflows):**
|
||||||
|
```typescript
|
||||||
|
function layoutThrashing(element: HTMLElement) {
|
||||||
|
element.style.width = '100px'
|
||||||
|
const width = element.offsetWidth // Forces reflow
|
||||||
|
element.style.height = '200px'
|
||||||
|
const height = element.offsetHeight // Forces another reflow
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (batch writes, then read once):**
|
||||||
|
```typescript
|
||||||
|
function updateElementStyles(element: HTMLElement) {
|
||||||
|
// Batch all writes together
|
||||||
|
element.style.width = '100px'
|
||||||
|
element.style.height = '200px'
|
||||||
|
element.style.backgroundColor = 'blue'
|
||||||
|
element.style.border = '1px solid black'
|
||||||
|
|
||||||
|
// Read after all writes are done (single reflow)
|
||||||
|
const { width, height } = element.getBoundingClientRect()
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (batch reads, then writes):**
|
||||||
|
```typescript
|
||||||
|
function avoidThrashing(element: HTMLElement) {
|
||||||
|
// Read phase - all layout queries first
|
||||||
|
const rect1 = element.getBoundingClientRect()
|
||||||
|
const offsetWidth = element.offsetWidth
|
||||||
|
const offsetHeight = element.offsetHeight
|
||||||
|
|
||||||
|
// Write phase - all style changes after
|
||||||
|
element.style.width = '100px'
|
||||||
|
element.style.height = '200px'
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Better: use CSS classes**
|
||||||
|
```css
|
||||||
|
.highlighted-box {
|
||||||
|
width: 100px;
|
||||||
|
height: 200px;
|
||||||
|
background-color: blue;
|
||||||
|
border: 1px solid black;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
```typescript
|
||||||
|
function updateElementStyles(element: HTMLElement) {
|
||||||
|
element.classList.add('highlighted-box')
|
||||||
|
|
||||||
|
const { width, height } = element.getBoundingClientRect()
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**React example:**
|
||||||
|
```tsx
|
||||||
|
// Incorrect: interleaving style changes with layout queries
|
||||||
|
function Box({ isHighlighted }: { isHighlighted: boolean }) {
|
||||||
|
const ref = useRef<HTMLDivElement>(null)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
if (ref.current && isHighlighted) {
|
||||||
|
ref.current.style.width = '100px'
|
||||||
|
const width = ref.current.offsetWidth // Forces layout
|
||||||
|
ref.current.style.height = '200px'
|
||||||
|
}
|
||||||
|
}, [isHighlighted])
|
||||||
|
|
||||||
|
return <div ref={ref}>Content</div>
|
||||||
|
}
|
||||||
|
|
||||||
|
// Correct: toggle class
|
||||||
|
function Box({ isHighlighted }: { isHighlighted: boolean }) {
|
||||||
|
return (
|
||||||
|
<div className={isHighlighted ? 'highlighted-box' : ''}>
|
||||||
|
Content
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Prefer CSS classes over inline styles when possible. CSS files are cached by the browser, and classes provide better separation of concerns and are easier to maintain.
|
||||||
|
|
||||||
|
See [this gist](https://gist.github.com/paulirish/5d52fb081b3570c81e3a) and [CSS Triggers](https://csstriggers.com/) for more information on layout-forcing operations.
|
||||||
@@ -0,0 +1,80 @@
|
|||||||
|
---
|
||||||
|
title: Cache Repeated Function Calls
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoid redundant computation
|
||||||
|
tags: javascript, cache, memoization, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Cache Repeated Function Calls
|
||||||
|
|
||||||
|
Use a module-level Map to cache function results when the same function is called repeatedly with the same inputs during render.
|
||||||
|
|
||||||
|
**Incorrect (redundant computation):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function ProjectList({ projects }: { projects: Project[] }) {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{projects.map(project => {
|
||||||
|
// slugify() called 100+ times for same project names
|
||||||
|
const slug = slugify(project.name)
|
||||||
|
|
||||||
|
return <ProjectCard key={project.id} slug={slug} />
|
||||||
|
})}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (cached results):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Module-level cache
|
||||||
|
const slugifyCache = new Map<string, string>()
|
||||||
|
|
||||||
|
function cachedSlugify(text: string): string {
|
||||||
|
if (slugifyCache.has(text)) {
|
||||||
|
return slugifyCache.get(text)!
|
||||||
|
}
|
||||||
|
const result = slugify(text)
|
||||||
|
slugifyCache.set(text, result)
|
||||||
|
return result
|
||||||
|
}
|
||||||
|
|
||||||
|
function ProjectList({ projects }: { projects: Project[] }) {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{projects.map(project => {
|
||||||
|
// Computed only once per unique project name
|
||||||
|
const slug = cachedSlugify(project.name)
|
||||||
|
|
||||||
|
return <ProjectCard key={project.id} slug={slug} />
|
||||||
|
})}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Simpler pattern for single-value functions:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
let isLoggedInCache: boolean | null = null
|
||||||
|
|
||||||
|
function isLoggedIn(): boolean {
|
||||||
|
if (isLoggedInCache !== null) {
|
||||||
|
return isLoggedInCache
|
||||||
|
}
|
||||||
|
|
||||||
|
isLoggedInCache = document.cookie.includes('auth=')
|
||||||
|
return isLoggedInCache
|
||||||
|
}
|
||||||
|
|
||||||
|
// Clear cache when auth changes
|
||||||
|
function onAuthChange() {
|
||||||
|
isLoggedInCache = null
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Use a Map (not a hook) so it works everywhere: utilities, event handlers, not just React components.
|
||||||
|
|
||||||
|
Reference: [How we made the Vercel Dashboard twice as fast](https://vercel.com/blog/how-we-made-the-vercel-dashboard-twice-as-fast)
|
||||||
@@ -0,0 +1,28 @@
|
|||||||
|
---
|
||||||
|
title: Cache Property Access in Loops
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: reduces lookups
|
||||||
|
tags: javascript, loops, optimization, caching
|
||||||
|
---
|
||||||
|
|
||||||
|
## Cache Property Access in Loops
|
||||||
|
|
||||||
|
Cache object property lookups in hot paths.
|
||||||
|
|
||||||
|
**Incorrect (3 lookups × N iterations):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
for (let i = 0; i < arr.length; i++) {
|
||||||
|
process(obj.config.settings.value)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (1 lookup total):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const value = obj.config.settings.value
|
||||||
|
const len = arr.length
|
||||||
|
for (let i = 0; i < len; i++) {
|
||||||
|
process(value)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,70 @@
|
|||||||
|
---
|
||||||
|
title: Cache Storage API Calls
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: reduces expensive I/O
|
||||||
|
tags: javascript, localStorage, storage, caching, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Cache Storage API Calls
|
||||||
|
|
||||||
|
`localStorage`, `sessionStorage`, and `document.cookie` are synchronous and expensive. Cache reads in memory.
|
||||||
|
|
||||||
|
**Incorrect (reads storage on every call):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function getTheme() {
|
||||||
|
return localStorage.getItem('theme') ?? 'light'
|
||||||
|
}
|
||||||
|
// Called 10 times = 10 storage reads
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (Map cache):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const storageCache = new Map<string, string | null>()
|
||||||
|
|
||||||
|
function getLocalStorage(key: string) {
|
||||||
|
if (!storageCache.has(key)) {
|
||||||
|
storageCache.set(key, localStorage.getItem(key))
|
||||||
|
}
|
||||||
|
return storageCache.get(key)
|
||||||
|
}
|
||||||
|
|
||||||
|
function setLocalStorage(key: string, value: string) {
|
||||||
|
localStorage.setItem(key, value)
|
||||||
|
storageCache.set(key, value) // keep cache in sync
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Use a Map (not a hook) so it works everywhere: utilities, event handlers, not just React components.
|
||||||
|
|
||||||
|
**Cookie caching:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
let cookieCache: Record<string, string> | null = null
|
||||||
|
|
||||||
|
function getCookie(name: string) {
|
||||||
|
if (!cookieCache) {
|
||||||
|
cookieCache = Object.fromEntries(
|
||||||
|
document.cookie.split('; ').map(c => c.split('='))
|
||||||
|
)
|
||||||
|
}
|
||||||
|
return cookieCache[name]
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Important (invalidate on external changes):**
|
||||||
|
|
||||||
|
If storage can change externally (another tab, server-set cookies), invalidate cache:
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
window.addEventListener('storage', (e) => {
|
||||||
|
if (e.key) storageCache.delete(e.key)
|
||||||
|
})
|
||||||
|
|
||||||
|
document.addEventListener('visibilitychange', () => {
|
||||||
|
if (document.visibilityState === 'visible') {
|
||||||
|
storageCache.clear()
|
||||||
|
}
|
||||||
|
})
|
||||||
|
```
|
||||||
@@ -0,0 +1,32 @@
|
|||||||
|
---
|
||||||
|
title: Combine Multiple Array Iterations
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: reduces iterations
|
||||||
|
tags: javascript, arrays, loops, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Combine Multiple Array Iterations
|
||||||
|
|
||||||
|
Multiple `.filter()` or `.map()` calls iterate the array multiple times. Combine into one loop.
|
||||||
|
|
||||||
|
**Incorrect (3 iterations):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const admins = users.filter(u => u.isAdmin)
|
||||||
|
const testers = users.filter(u => u.isTester)
|
||||||
|
const inactive = users.filter(u => !u.isActive)
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (1 iteration):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const admins: User[] = []
|
||||||
|
const testers: User[] = []
|
||||||
|
const inactive: User[] = []
|
||||||
|
|
||||||
|
for (const user of users) {
|
||||||
|
if (user.isAdmin) admins.push(user)
|
||||||
|
if (user.isTester) testers.push(user)
|
||||||
|
if (!user.isActive) inactive.push(user)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,50 @@
|
|||||||
|
---
|
||||||
|
title: Early Return from Functions
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: avoids unnecessary computation
|
||||||
|
tags: javascript, functions, optimization, early-return
|
||||||
|
---
|
||||||
|
|
||||||
|
## Early Return from Functions
|
||||||
|
|
||||||
|
Return early when result is determined to skip unnecessary processing.
|
||||||
|
|
||||||
|
**Incorrect (processes all items even after finding answer):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function validateUsers(users: User[]) {
|
||||||
|
let hasError = false
|
||||||
|
let errorMessage = ''
|
||||||
|
|
||||||
|
for (const user of users) {
|
||||||
|
if (!user.email) {
|
||||||
|
hasError = true
|
||||||
|
errorMessage = 'Email required'
|
||||||
|
}
|
||||||
|
if (!user.name) {
|
||||||
|
hasError = true
|
||||||
|
errorMessage = 'Name required'
|
||||||
|
}
|
||||||
|
// Continues checking all users even after error found
|
||||||
|
}
|
||||||
|
|
||||||
|
return hasError ? { valid: false, error: errorMessage } : { valid: true }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (returns immediately on first error):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function validateUsers(users: User[]) {
|
||||||
|
for (const user of users) {
|
||||||
|
if (!user.email) {
|
||||||
|
return { valid: false, error: 'Email required' }
|
||||||
|
}
|
||||||
|
if (!user.name) {
|
||||||
|
return { valid: false, error: 'Name required' }
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return { valid: true }
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,45 @@
|
|||||||
|
---
|
||||||
|
title: Hoist RegExp Creation
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: avoids recreation
|
||||||
|
tags: javascript, regexp, optimization, memoization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Hoist RegExp Creation
|
||||||
|
|
||||||
|
Don't create RegExp inside render. Hoist to module scope or memoize with `useMemo()`.
|
||||||
|
|
||||||
|
**Incorrect (new RegExp every render):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Highlighter({ text, query }: Props) {
|
||||||
|
const regex = new RegExp(`(${query})`, 'gi')
|
||||||
|
const parts = text.split(regex)
|
||||||
|
return <>{parts.map((part, i) => ...)}</>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (memoize or hoist):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
const EMAIL_REGEX = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
|
||||||
|
|
||||||
|
function Highlighter({ text, query }: Props) {
|
||||||
|
const regex = useMemo(
|
||||||
|
() => new RegExp(`(${escapeRegex(query)})`, 'gi'),
|
||||||
|
[query]
|
||||||
|
)
|
||||||
|
const parts = text.split(regex)
|
||||||
|
return <>{parts.map((part, i) => ...)}</>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Warning (global regex has mutable state):**
|
||||||
|
|
||||||
|
Global regex (`/g`) has mutable `lastIndex` state:
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const regex = /foo/g
|
||||||
|
regex.test('foo') // true, lastIndex = 3
|
||||||
|
regex.test('foo') // false, lastIndex = 0
|
||||||
|
```
|
||||||
@@ -0,0 +1,37 @@
|
|||||||
|
---
|
||||||
|
title: Build Index Maps for Repeated Lookups
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: 1M ops to 2K ops
|
||||||
|
tags: javascript, map, indexing, optimization, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Build Index Maps for Repeated Lookups
|
||||||
|
|
||||||
|
Multiple `.find()` calls by the same key should use a Map.
|
||||||
|
|
||||||
|
**Incorrect (O(n) per lookup):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function processOrders(orders: Order[], users: User[]) {
|
||||||
|
return orders.map(order => ({
|
||||||
|
...order,
|
||||||
|
user: users.find(u => u.id === order.userId)
|
||||||
|
}))
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (O(1) per lookup):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function processOrders(orders: Order[], users: User[]) {
|
||||||
|
const userById = new Map(users.map(u => [u.id, u]))
|
||||||
|
|
||||||
|
return orders.map(order => ({
|
||||||
|
...order,
|
||||||
|
user: userById.get(order.userId)
|
||||||
|
}))
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Build map once (O(n)), then all lookups are O(1).
|
||||||
|
For 1000 orders × 1000 users: 1M ops → 2K ops.
|
||||||
@@ -0,0 +1,49 @@
|
|||||||
|
---
|
||||||
|
title: Early Length Check for Array Comparisons
|
||||||
|
impact: MEDIUM-HIGH
|
||||||
|
impactDescription: avoids expensive operations when lengths differ
|
||||||
|
tags: javascript, arrays, performance, optimization, comparison
|
||||||
|
---
|
||||||
|
|
||||||
|
## Early Length Check for Array Comparisons
|
||||||
|
|
||||||
|
When comparing arrays with expensive operations (sorting, deep equality, serialization), check lengths first. If lengths differ, the arrays cannot be equal.
|
||||||
|
|
||||||
|
In real-world applications, this optimization is especially valuable when the comparison runs in hot paths (event handlers, render loops).
|
||||||
|
|
||||||
|
**Incorrect (always runs expensive comparison):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function hasChanges(current: string[], original: string[]) {
|
||||||
|
// Always sorts and joins, even when lengths differ
|
||||||
|
return current.sort().join() !== original.sort().join()
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Two O(n log n) sorts run even when `current.length` is 5 and `original.length` is 100. There is also overhead of joining the arrays and comparing the strings.
|
||||||
|
|
||||||
|
**Correct (O(1) length check first):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function hasChanges(current: string[], original: string[]) {
|
||||||
|
// Early return if lengths differ
|
||||||
|
if (current.length !== original.length) {
|
||||||
|
return true
|
||||||
|
}
|
||||||
|
// Only sort when lengths match
|
||||||
|
const currentSorted = current.toSorted()
|
||||||
|
const originalSorted = original.toSorted()
|
||||||
|
for (let i = 0; i < currentSorted.length; i++) {
|
||||||
|
if (currentSorted[i] !== originalSorted[i]) {
|
||||||
|
return true
|
||||||
|
}
|
||||||
|
}
|
||||||
|
return false
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
This new approach is more efficient because:
|
||||||
|
- It avoids the overhead of sorting and joining the arrays when lengths differ
|
||||||
|
- It avoids consuming memory for the joined strings (especially important for large arrays)
|
||||||
|
- It avoids mutating the original arrays
|
||||||
|
- It returns early when a difference is found
|
||||||
@@ -0,0 +1,82 @@
|
|||||||
|
---
|
||||||
|
title: Use Loop for Min/Max Instead of Sort
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: O(n) instead of O(n log n)
|
||||||
|
tags: javascript, arrays, performance, sorting, algorithms
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Loop for Min/Max Instead of Sort
|
||||||
|
|
||||||
|
Finding the smallest or largest element only requires a single pass through the array. Sorting is wasteful and slower.
|
||||||
|
|
||||||
|
**Incorrect (O(n log n) - sort to find latest):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
interface Project {
|
||||||
|
id: string
|
||||||
|
name: string
|
||||||
|
updatedAt: number
|
||||||
|
}
|
||||||
|
|
||||||
|
function getLatestProject(projects: Project[]) {
|
||||||
|
const sorted = [...projects].sort((a, b) => b.updatedAt - a.updatedAt)
|
||||||
|
return sorted[0]
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Sorts the entire array just to find the maximum value.
|
||||||
|
|
||||||
|
**Incorrect (O(n log n) - sort for oldest and newest):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function getOldestAndNewest(projects: Project[]) {
|
||||||
|
const sorted = [...projects].sort((a, b) => a.updatedAt - b.updatedAt)
|
||||||
|
return { oldest: sorted[0], newest: sorted[sorted.length - 1] }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Still sorts unnecessarily when only min/max are needed.
|
||||||
|
|
||||||
|
**Correct (O(n) - single loop):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function getLatestProject(projects: Project[]) {
|
||||||
|
if (projects.length === 0) return null
|
||||||
|
|
||||||
|
let latest = projects[0]
|
||||||
|
|
||||||
|
for (let i = 1; i < projects.length; i++) {
|
||||||
|
if (projects[i].updatedAt > latest.updatedAt) {
|
||||||
|
latest = projects[i]
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return latest
|
||||||
|
}
|
||||||
|
|
||||||
|
function getOldestAndNewest(projects: Project[]) {
|
||||||
|
if (projects.length === 0) return { oldest: null, newest: null }
|
||||||
|
|
||||||
|
let oldest = projects[0]
|
||||||
|
let newest = projects[0]
|
||||||
|
|
||||||
|
for (let i = 1; i < projects.length; i++) {
|
||||||
|
if (projects[i].updatedAt < oldest.updatedAt) oldest = projects[i]
|
||||||
|
if (projects[i].updatedAt > newest.updatedAt) newest = projects[i]
|
||||||
|
}
|
||||||
|
|
||||||
|
return { oldest, newest }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Single pass through the array, no copying, no sorting.
|
||||||
|
|
||||||
|
**Alternative (Math.min/Math.max for small arrays):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const numbers = [5, 2, 8, 1, 9]
|
||||||
|
const min = Math.min(...numbers)
|
||||||
|
const max = Math.max(...numbers)
|
||||||
|
```
|
||||||
|
|
||||||
|
This works for small arrays, but can be slower or just throw an error for very large arrays due to spread operator limitations. Maximal array length is approximately 124000 in Chrome 143 and 638000 in Safari 18; exact numbers may vary - see [the fiddle](https://jsfiddle.net/qw1jabsx/4/). Use the loop approach for reliability.
|
||||||
@@ -0,0 +1,24 @@
|
|||||||
|
---
|
||||||
|
title: Use Set/Map for O(1) Lookups
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: O(n) to O(1)
|
||||||
|
tags: javascript, set, map, data-structures, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Set/Map for O(1) Lookups
|
||||||
|
|
||||||
|
Convert arrays to Set/Map for repeated membership checks.
|
||||||
|
|
||||||
|
**Incorrect (O(n) per check):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const allowedIds = ['a', 'b', 'c', ...]
|
||||||
|
items.filter(item => allowedIds.includes(item.id))
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (O(1) per check):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const allowedIds = new Set(['a', 'b', 'c', ...])
|
||||||
|
items.filter(item => allowedIds.has(item.id))
|
||||||
|
```
|
||||||
@@ -0,0 +1,57 @@
|
|||||||
|
---
|
||||||
|
title: Use toSorted() Instead of sort() for Immutability
|
||||||
|
impact: MEDIUM-HIGH
|
||||||
|
impactDescription: prevents mutation bugs in React state
|
||||||
|
tags: javascript, arrays, immutability, react, state, mutation
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use toSorted() Instead of sort() for Immutability
|
||||||
|
|
||||||
|
`.sort()` mutates the array in place, which can cause bugs with React state and props. Use `.toSorted()` to create a new sorted array without mutation.
|
||||||
|
|
||||||
|
**Incorrect (mutates original array):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function UserList({ users }: { users: User[] }) {
|
||||||
|
// Mutates the users prop array!
|
||||||
|
const sorted = useMemo(
|
||||||
|
() => users.sort((a, b) => a.name.localeCompare(b.name)),
|
||||||
|
[users]
|
||||||
|
)
|
||||||
|
return <div>{sorted.map(renderUser)}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (creates new array):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
function UserList({ users }: { users: User[] }) {
|
||||||
|
// Creates new sorted array, original unchanged
|
||||||
|
const sorted = useMemo(
|
||||||
|
() => users.toSorted((a, b) => a.name.localeCompare(b.name)),
|
||||||
|
[users]
|
||||||
|
)
|
||||||
|
return <div>{sorted.map(renderUser)}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Why this matters in React:**
|
||||||
|
|
||||||
|
1. Props/state mutations break React's immutability model - React expects props and state to be treated as read-only
|
||||||
|
2. Causes stale closure bugs - Mutating arrays inside closures (callbacks, effects) can lead to unexpected behavior
|
||||||
|
|
||||||
|
**Browser support (fallback for older browsers):**
|
||||||
|
|
||||||
|
`.toSorted()` is available in all modern browsers (Chrome 110+, Safari 16+, Firefox 115+, Node.js 20+). For older environments, use spread operator:
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
// Fallback for older browsers
|
||||||
|
const sorted = [...items].sort((a, b) => a.value - b.value)
|
||||||
|
```
|
||||||
|
|
||||||
|
**Other immutable array methods:**
|
||||||
|
|
||||||
|
- `.toSorted()` - immutable sort
|
||||||
|
- `.toReversed()` - immutable reverse
|
||||||
|
- `.toSpliced()` - immutable splice
|
||||||
|
- `.with()` - immutable element replacement
|
||||||
@@ -0,0 +1,26 @@
|
|||||||
|
---
|
||||||
|
title: Use Activity Component for Show/Hide
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: preserves state/DOM
|
||||||
|
tags: rendering, activity, visibility, state-preservation
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Activity Component for Show/Hide
|
||||||
|
|
||||||
|
Use React's `<Activity>` to preserve state/DOM for expensive components that frequently toggle visibility.
|
||||||
|
|
||||||
|
**Usage:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { Activity } from 'react'
|
||||||
|
|
||||||
|
function Dropdown({ isOpen }: Props) {
|
||||||
|
return (
|
||||||
|
<Activity mode={isOpen ? 'visible' : 'hidden'}>
|
||||||
|
<ExpensiveMenu />
|
||||||
|
</Activity>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Avoids expensive re-renders and state loss.
|
||||||
@@ -0,0 +1,47 @@
|
|||||||
|
---
|
||||||
|
title: Animate SVG Wrapper Instead of SVG Element
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: enables hardware acceleration
|
||||||
|
tags: rendering, svg, css, animation, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Animate SVG Wrapper Instead of SVG Element
|
||||||
|
|
||||||
|
Many browsers don't have hardware acceleration for CSS3 animations on SVG elements. Wrap SVG in a `<div>` and animate the wrapper instead.
|
||||||
|
|
||||||
|
**Incorrect (animating SVG directly - no hardware acceleration):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function LoadingSpinner() {
|
||||||
|
return (
|
||||||
|
<svg
|
||||||
|
className="animate-spin"
|
||||||
|
width="24"
|
||||||
|
height="24"
|
||||||
|
viewBox="0 0 24 24"
|
||||||
|
>
|
||||||
|
<circle cx="12" cy="12" r="10" stroke="currentColor" />
|
||||||
|
</svg>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (animating wrapper div - hardware accelerated):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function LoadingSpinner() {
|
||||||
|
return (
|
||||||
|
<div className="animate-spin">
|
||||||
|
<svg
|
||||||
|
width="24"
|
||||||
|
height="24"
|
||||||
|
viewBox="0 0 24 24"
|
||||||
|
>
|
||||||
|
<circle cx="12" cy="12" r="10" stroke="currentColor" />
|
||||||
|
</svg>
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
This applies to all CSS transforms and transitions (`transform`, `opacity`, `translate`, `scale`, `rotate`). The wrapper div allows browsers to use GPU acceleration for smoother animations.
|
||||||
@@ -0,0 +1,40 @@
|
|||||||
|
---
|
||||||
|
title: Use Explicit Conditional Rendering
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: prevents rendering 0 or NaN
|
||||||
|
tags: rendering, conditional, jsx, falsy-values
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Explicit Conditional Rendering
|
||||||
|
|
||||||
|
Use explicit ternary operators (`? :`) instead of `&&` for conditional rendering when the condition can be `0`, `NaN`, or other falsy values that render.
|
||||||
|
|
||||||
|
**Incorrect (renders "0" when count is 0):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Badge({ count }: { count: number }) {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{count && <span className="badge">{count}</span>}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
// When count = 0, renders: <div>0</div>
|
||||||
|
// When count = 5, renders: <div><span class="badge">5</span></div>
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (renders nothing when count is 0):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Badge({ count }: { count: number }) {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{count > 0 ? <span className="badge">{count}</span> : null}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
// When count = 0, renders: <div></div>
|
||||||
|
// When count = 5, renders: <div><span class="badge">5</span></div>
|
||||||
|
```
|
||||||
@@ -0,0 +1,38 @@
|
|||||||
|
---
|
||||||
|
title: CSS content-visibility for Long Lists
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: faster initial render
|
||||||
|
tags: rendering, css, content-visibility, long-lists
|
||||||
|
---
|
||||||
|
|
||||||
|
## CSS content-visibility for Long Lists
|
||||||
|
|
||||||
|
Apply `content-visibility: auto` to defer off-screen rendering.
|
||||||
|
|
||||||
|
**CSS:**
|
||||||
|
|
||||||
|
```css
|
||||||
|
.message-item {
|
||||||
|
content-visibility: auto;
|
||||||
|
contain-intrinsic-size: 0 80px;
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Example:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function MessageList({ messages }: { messages: Message[] }) {
|
||||||
|
return (
|
||||||
|
<div className="overflow-y-auto h-screen">
|
||||||
|
{messages.map(msg => (
|
||||||
|
<div key={msg.id} className="message-item">
|
||||||
|
<Avatar user={msg.author} />
|
||||||
|
<div>{msg.content}</div>
|
||||||
|
</div>
|
||||||
|
))}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
For 1000 messages, browser skips layout/paint for ~990 off-screen items (10× faster initial render).
|
||||||
@@ -0,0 +1,46 @@
|
|||||||
|
---
|
||||||
|
title: Hoist Static JSX Elements
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: avoids re-creation
|
||||||
|
tags: rendering, jsx, static, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Hoist Static JSX Elements
|
||||||
|
|
||||||
|
Extract static JSX outside components to avoid re-creation.
|
||||||
|
|
||||||
|
**Incorrect (recreates element every render):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function LoadingSkeleton() {
|
||||||
|
return <div className="animate-pulse h-20 bg-gray-200" />
|
||||||
|
}
|
||||||
|
|
||||||
|
function Container() {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{loading && <LoadingSkeleton />}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (reuses same element):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
const loadingSkeleton = (
|
||||||
|
<div className="animate-pulse h-20 bg-gray-200" />
|
||||||
|
)
|
||||||
|
|
||||||
|
function Container() {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
{loading && loadingSkeleton}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
This is especially helpful for large and static SVG nodes, which can be expensive to recreate on every render.
|
||||||
|
|
||||||
|
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, the compiler automatically hoists static JSX elements and optimizes component re-renders, making manual hoisting unnecessary.
|
||||||
@@ -0,0 +1,82 @@
|
|||||||
|
---
|
||||||
|
title: Prevent Hydration Mismatch Without Flickering
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoids visual flicker and hydration errors
|
||||||
|
tags: rendering, ssr, hydration, localStorage, flicker
|
||||||
|
---
|
||||||
|
|
||||||
|
## Prevent Hydration Mismatch Without Flickering
|
||||||
|
|
||||||
|
When rendering content that depends on client-side storage (localStorage, cookies), avoid both SSR breakage and post-hydration flickering by injecting a synchronous script that updates the DOM before React hydrates.
|
||||||
|
|
||||||
|
**Incorrect (breaks SSR):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||||
|
// localStorage is not available on server - throws error
|
||||||
|
const theme = localStorage.getItem('theme') || 'light'
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div className={theme}>
|
||||||
|
{children}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Server-side rendering will fail because `localStorage` is undefined.
|
||||||
|
|
||||||
|
**Incorrect (visual flickering):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||||
|
const [theme, setTheme] = useState('light')
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
// Runs after hydration - causes visible flash
|
||||||
|
const stored = localStorage.getItem('theme')
|
||||||
|
if (stored) {
|
||||||
|
setTheme(stored)
|
||||||
|
}
|
||||||
|
}, [])
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div className={theme}>
|
||||||
|
{children}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Component first renders with default value (`light`), then updates after hydration, causing a visible flash of incorrect content.
|
||||||
|
|
||||||
|
**Correct (no flicker, no hydration mismatch):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||||
|
return (
|
||||||
|
<>
|
||||||
|
<div id="theme-wrapper">
|
||||||
|
{children}
|
||||||
|
</div>
|
||||||
|
<script
|
||||||
|
dangerouslySetInnerHTML={{
|
||||||
|
__html: `
|
||||||
|
(function() {
|
||||||
|
try {
|
||||||
|
var theme = localStorage.getItem('theme') || 'light';
|
||||||
|
var el = document.getElementById('theme-wrapper');
|
||||||
|
if (el) el.className = theme;
|
||||||
|
} catch (e) {}
|
||||||
|
})();
|
||||||
|
`,
|
||||||
|
}}
|
||||||
|
/>
|
||||||
|
</>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The inline script executes synchronously before showing the element, ensuring the DOM already has the correct value. No flickering, no hydration mismatch.
|
||||||
|
|
||||||
|
This pattern is especially useful for theme toggles, user preferences, authentication states, and any client-only data that should render immediately without flashing default values.
|
||||||
@@ -0,0 +1,30 @@
|
|||||||
|
---
|
||||||
|
title: Suppress Expected Hydration Mismatches
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: avoids noisy hydration warnings for known differences
|
||||||
|
tags: rendering, hydration, ssr, nextjs
|
||||||
|
---
|
||||||
|
|
||||||
|
## Suppress Expected Hydration Mismatches
|
||||||
|
|
||||||
|
In SSR frameworks (e.g., Next.js), some values are intentionally different on server vs client (random IDs, dates, locale/timezone formatting). For these *expected* mismatches, wrap the dynamic text in an element with `suppressHydrationWarning` to prevent noisy warnings. Do not use this to hide real bugs. Don’t overuse it.
|
||||||
|
|
||||||
|
**Incorrect (known mismatch warnings):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Timestamp() {
|
||||||
|
return <span>{new Date().toLocaleString()}</span>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (suppress expected mismatch only):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Timestamp() {
|
||||||
|
return (
|
||||||
|
<span suppressHydrationWarning>
|
||||||
|
{new Date().toLocaleString()}
|
||||||
|
</span>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,28 @@
|
|||||||
|
---
|
||||||
|
title: Optimize SVG Precision
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: reduces file size
|
||||||
|
tags: rendering, svg, optimization, svgo
|
||||||
|
---
|
||||||
|
|
||||||
|
## Optimize SVG Precision
|
||||||
|
|
||||||
|
Reduce SVG coordinate precision to decrease file size. The optimal precision depends on the viewBox size, but in general reducing precision should be considered.
|
||||||
|
|
||||||
|
**Incorrect (excessive precision):**
|
||||||
|
|
||||||
|
```svg
|
||||||
|
<path d="M 10.293847 20.847362 L 30.938472 40.192837" />
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (1 decimal place):**
|
||||||
|
|
||||||
|
```svg
|
||||||
|
<path d="M 10.3 20.8 L 30.9 40.2" />
|
||||||
|
```
|
||||||
|
|
||||||
|
**Automate with SVGO:**
|
||||||
|
|
||||||
|
```bash
|
||||||
|
npx svgo --precision=1 --multipass icon.svg
|
||||||
|
```
|
||||||
@@ -0,0 +1,75 @@
|
|||||||
|
---
|
||||||
|
title: Use useTransition Over Manual Loading States
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: reduces re-renders and improves code clarity
|
||||||
|
tags: rendering, transitions, useTransition, loading, state
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use useTransition Over Manual Loading States
|
||||||
|
|
||||||
|
Use `useTransition` instead of manual `useState` for loading states. This provides built-in `isPending` state and automatically manages transitions.
|
||||||
|
|
||||||
|
**Incorrect (manual loading state):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function SearchResults() {
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
const [results, setResults] = useState([])
|
||||||
|
const [isLoading, setIsLoading] = useState(false)
|
||||||
|
|
||||||
|
const handleSearch = async (value: string) => {
|
||||||
|
setIsLoading(true)
|
||||||
|
setQuery(value)
|
||||||
|
const data = await fetchResults(value)
|
||||||
|
setResults(data)
|
||||||
|
setIsLoading(false)
|
||||||
|
}
|
||||||
|
|
||||||
|
return (
|
||||||
|
<>
|
||||||
|
<input onChange={(e) => handleSearch(e.target.value)} />
|
||||||
|
{isLoading && <Spinner />}
|
||||||
|
<ResultsList results={results} />
|
||||||
|
</>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (useTransition with built-in pending state):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { useTransition, useState } from 'react'
|
||||||
|
|
||||||
|
function SearchResults() {
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
const [results, setResults] = useState([])
|
||||||
|
const [isPending, startTransition] = useTransition()
|
||||||
|
|
||||||
|
const handleSearch = (value: string) => {
|
||||||
|
setQuery(value) // Update input immediately
|
||||||
|
|
||||||
|
startTransition(async () => {
|
||||||
|
// Fetch and update results
|
||||||
|
const data = await fetchResults(value)
|
||||||
|
setResults(data)
|
||||||
|
})
|
||||||
|
}
|
||||||
|
|
||||||
|
return (
|
||||||
|
<>
|
||||||
|
<input onChange={(e) => handleSearch(e.target.value)} />
|
||||||
|
{isPending && <Spinner />}
|
||||||
|
<ResultsList results={results} />
|
||||||
|
</>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Benefits:**
|
||||||
|
|
||||||
|
- **Automatic pending state**: No need to manually manage `setIsLoading(true/false)`
|
||||||
|
- **Error resilience**: Pending state correctly resets even if the transition throws
|
||||||
|
- **Better responsiveness**: Keeps the UI responsive during updates
|
||||||
|
- **Interrupt handling**: New transitions automatically cancel pending ones
|
||||||
|
|
||||||
|
Reference: [useTransition](https://react.dev/reference/react/useTransition)
|
||||||
@@ -0,0 +1,39 @@
|
|||||||
|
---
|
||||||
|
title: Defer State Reads to Usage Point
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoids unnecessary subscriptions
|
||||||
|
tags: rerender, searchParams, localStorage, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Defer State Reads to Usage Point
|
||||||
|
|
||||||
|
Don't subscribe to dynamic state (searchParams, localStorage) if you only read it inside callbacks.
|
||||||
|
|
||||||
|
**Incorrect (subscribes to all searchParams changes):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ShareButton({ chatId }: { chatId: string }) {
|
||||||
|
const searchParams = useSearchParams()
|
||||||
|
|
||||||
|
const handleShare = () => {
|
||||||
|
const ref = searchParams.get('ref')
|
||||||
|
shareChat(chatId, { ref })
|
||||||
|
}
|
||||||
|
|
||||||
|
return <button onClick={handleShare}>Share</button>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (reads on demand, no subscription):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ShareButton({ chatId }: { chatId: string }) {
|
||||||
|
const handleShare = () => {
|
||||||
|
const params = new URLSearchParams(window.location.search)
|
||||||
|
const ref = params.get('ref')
|
||||||
|
shareChat(chatId, { ref })
|
||||||
|
}
|
||||||
|
|
||||||
|
return <button onClick={handleShare}>Share</button>
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,45 @@
|
|||||||
|
---
|
||||||
|
title: Narrow Effect Dependencies
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: minimizes effect re-runs
|
||||||
|
tags: rerender, useEffect, dependencies, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Narrow Effect Dependencies
|
||||||
|
|
||||||
|
Specify primitive dependencies instead of objects to minimize effect re-runs.
|
||||||
|
|
||||||
|
**Incorrect (re-runs on any user field change):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
useEffect(() => {
|
||||||
|
console.log(user.id)
|
||||||
|
}, [user])
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (re-runs only when id changes):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
useEffect(() => {
|
||||||
|
console.log(user.id)
|
||||||
|
}, [user.id])
|
||||||
|
```
|
||||||
|
|
||||||
|
**For derived state, compute outside effect:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
// Incorrect: runs on width=767, 766, 765...
|
||||||
|
useEffect(() => {
|
||||||
|
if (width < 768) {
|
||||||
|
enableMobileMode()
|
||||||
|
}
|
||||||
|
}, [width])
|
||||||
|
|
||||||
|
// Correct: runs only on boolean transition
|
||||||
|
const isMobile = width < 768
|
||||||
|
useEffect(() => {
|
||||||
|
if (isMobile) {
|
||||||
|
enableMobileMode()
|
||||||
|
}
|
||||||
|
}, [isMobile])
|
||||||
|
```
|
||||||
@@ -0,0 +1,40 @@
|
|||||||
|
---
|
||||||
|
title: Calculate Derived State During Rendering
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoids redundant renders and state drift
|
||||||
|
tags: rerender, derived-state, useEffect, state
|
||||||
|
---
|
||||||
|
|
||||||
|
## Calculate Derived State During Rendering
|
||||||
|
|
||||||
|
If a value can be computed from current props/state, do not store it in state or update it in an effect. Derive it during render to avoid extra renders and state drift. Do not set state in effects solely in response to prop changes; prefer derived values or keyed resets instead.
|
||||||
|
|
||||||
|
**Incorrect (redundant state and effect):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Form() {
|
||||||
|
const [firstName, setFirstName] = useState('First')
|
||||||
|
const [lastName, setLastName] = useState('Last')
|
||||||
|
const [fullName, setFullName] = useState('')
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
setFullName(firstName + ' ' + lastName)
|
||||||
|
}, [firstName, lastName])
|
||||||
|
|
||||||
|
return <p>{fullName}</p>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (derive during render):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Form() {
|
||||||
|
const [firstName, setFirstName] = useState('First')
|
||||||
|
const [lastName, setLastName] = useState('Last')
|
||||||
|
const fullName = firstName + ' ' + lastName
|
||||||
|
|
||||||
|
return <p>{fullName}</p>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
References: [You Might Not Need an Effect](https://react.dev/learn/you-might-not-need-an-effect)
|
||||||
@@ -0,0 +1,29 @@
|
|||||||
|
---
|
||||||
|
title: Subscribe to Derived State
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: reduces re-render frequency
|
||||||
|
tags: rerender, derived-state, media-query, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Subscribe to Derived State
|
||||||
|
|
||||||
|
Subscribe to derived boolean state instead of continuous values to reduce re-render frequency.
|
||||||
|
|
||||||
|
**Incorrect (re-renders on every pixel change):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Sidebar() {
|
||||||
|
const width = useWindowWidth() // updates continuously
|
||||||
|
const isMobile = width < 768
|
||||||
|
return <nav className={isMobile ? 'mobile' : 'desktop'} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (re-renders only when boolean changes):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Sidebar() {
|
||||||
|
const isMobile = useMediaQuery('(max-width: 767px)')
|
||||||
|
return <nav className={isMobile ? 'mobile' : 'desktop'} />
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,74 @@
|
|||||||
|
---
|
||||||
|
title: Use Functional setState Updates
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: prevents stale closures and unnecessary callback recreations
|
||||||
|
tags: react, hooks, useState, useCallback, callbacks, closures
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Functional setState Updates
|
||||||
|
|
||||||
|
When updating state based on the current state value, use the functional update form of setState instead of directly referencing the state variable. This prevents stale closures, eliminates unnecessary dependencies, and creates stable callback references.
|
||||||
|
|
||||||
|
**Incorrect (requires state as dependency):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function TodoList() {
|
||||||
|
const [items, setItems] = useState(initialItems)
|
||||||
|
|
||||||
|
// Callback must depend on items, recreated on every items change
|
||||||
|
const addItems = useCallback((newItems: Item[]) => {
|
||||||
|
setItems([...items, ...newItems])
|
||||||
|
}, [items]) // ❌ items dependency causes recreations
|
||||||
|
|
||||||
|
// Risk of stale closure if dependency is forgotten
|
||||||
|
const removeItem = useCallback((id: string) => {
|
||||||
|
setItems(items.filter(item => item.id !== id))
|
||||||
|
}, []) // ❌ Missing items dependency - will use stale items!
|
||||||
|
|
||||||
|
return <ItemsEditor items={items} onAdd={addItems} onRemove={removeItem} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The first callback is recreated every time `items` changes, which can cause child components to re-render unnecessarily. The second callback has a stale closure bug—it will always reference the initial `items` value.
|
||||||
|
|
||||||
|
**Correct (stable callbacks, no stale closures):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function TodoList() {
|
||||||
|
const [items, setItems] = useState(initialItems)
|
||||||
|
|
||||||
|
// Stable callback, never recreated
|
||||||
|
const addItems = useCallback((newItems: Item[]) => {
|
||||||
|
setItems(curr => [...curr, ...newItems])
|
||||||
|
}, []) // ✅ No dependencies needed
|
||||||
|
|
||||||
|
// Always uses latest state, no stale closure risk
|
||||||
|
const removeItem = useCallback((id: string) => {
|
||||||
|
setItems(curr => curr.filter(item => item.id !== id))
|
||||||
|
}, []) // ✅ Safe and stable
|
||||||
|
|
||||||
|
return <ItemsEditor items={items} onAdd={addItems} onRemove={removeItem} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Benefits:**
|
||||||
|
|
||||||
|
1. **Stable callback references** - Callbacks don't need to be recreated when state changes
|
||||||
|
2. **No stale closures** - Always operates on the latest state value
|
||||||
|
3. **Fewer dependencies** - Simplifies dependency arrays and reduces memory leaks
|
||||||
|
4. **Prevents bugs** - Eliminates the most common source of React closure bugs
|
||||||
|
|
||||||
|
**When to use functional updates:**
|
||||||
|
|
||||||
|
- Any setState that depends on the current state value
|
||||||
|
- Inside useCallback/useMemo when state is needed
|
||||||
|
- Event handlers that reference state
|
||||||
|
- Async operations that update state
|
||||||
|
|
||||||
|
**When direct updates are fine:**
|
||||||
|
|
||||||
|
- Setting state to a static value: `setCount(0)`
|
||||||
|
- Setting state from props/arguments only: `setName(newName)`
|
||||||
|
- State doesn't depend on previous value
|
||||||
|
|
||||||
|
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, the compiler can automatically optimize some cases, but functional updates are still recommended for correctness and to prevent stale closure bugs.
|
||||||
@@ -0,0 +1,58 @@
|
|||||||
|
---
|
||||||
|
title: Use Lazy State Initialization
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: wasted computation on every render
|
||||||
|
tags: react, hooks, useState, performance, initialization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Lazy State Initialization
|
||||||
|
|
||||||
|
Pass a function to `useState` for expensive initial values. Without the function form, the initializer runs on every render even though the value is only used once.
|
||||||
|
|
||||||
|
**Incorrect (runs on every render):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function FilteredList({ items }: { items: Item[] }) {
|
||||||
|
// buildSearchIndex() runs on EVERY render, even after initialization
|
||||||
|
const [searchIndex, setSearchIndex] = useState(buildSearchIndex(items))
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
|
||||||
|
// When query changes, buildSearchIndex runs again unnecessarily
|
||||||
|
return <SearchResults index={searchIndex} query={query} />
|
||||||
|
}
|
||||||
|
|
||||||
|
function UserProfile() {
|
||||||
|
// JSON.parse runs on every render
|
||||||
|
const [settings, setSettings] = useState(
|
||||||
|
JSON.parse(localStorage.getItem('settings') || '{}')
|
||||||
|
)
|
||||||
|
|
||||||
|
return <SettingsForm settings={settings} onChange={setSettings} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (runs only once):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function FilteredList({ items }: { items: Item[] }) {
|
||||||
|
// buildSearchIndex() runs ONLY on initial render
|
||||||
|
const [searchIndex, setSearchIndex] = useState(() => buildSearchIndex(items))
|
||||||
|
const [query, setQuery] = useState('')
|
||||||
|
|
||||||
|
return <SearchResults index={searchIndex} query={query} />
|
||||||
|
}
|
||||||
|
|
||||||
|
function UserProfile() {
|
||||||
|
// JSON.parse runs only on initial render
|
||||||
|
const [settings, setSettings] = useState(() => {
|
||||||
|
const stored = localStorage.getItem('settings')
|
||||||
|
return stored ? JSON.parse(stored) : {}
|
||||||
|
})
|
||||||
|
|
||||||
|
return <SettingsForm settings={settings} onChange={setSettings} />
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Use lazy initialization when computing initial values from localStorage/sessionStorage, building data structures (indexes, maps), reading from the DOM, or performing heavy transformations.
|
||||||
|
|
||||||
|
For simple primitives (`useState(0)`), direct references (`useState(props.value)`), or cheap literals (`useState({})`), the function form is unnecessary.
|
||||||
@@ -0,0 +1,38 @@
|
|||||||
|
---
|
||||||
|
|
||||||
|
title: Extract Default Non-primitive Parameter Value from Memoized Component to Constant
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: restores memoization by using a constant for default value
|
||||||
|
tags: rerender, memo, optimization
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## Extract Default Non-primitive Parameter Value from Memoized Component to Constant
|
||||||
|
|
||||||
|
When memoized component has a default value for some non-primitive optional parameter, such as an array, function, or object, calling the component without that parameter results in broken memoization. This is because new value instances are created on every rerender, and they do not pass strict equality comparison in `memo()`.
|
||||||
|
|
||||||
|
To address this issue, extract the default value into a constant.
|
||||||
|
|
||||||
|
**Incorrect (`onClick` has different values on every rerender):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
const UserAvatar = memo(function UserAvatar({ onClick = () => {} }: { onClick?: () => void }) {
|
||||||
|
// ...
|
||||||
|
})
|
||||||
|
|
||||||
|
// Used without optional onClick
|
||||||
|
<UserAvatar />
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (stable default value):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
const NOOP = () => {};
|
||||||
|
|
||||||
|
const UserAvatar = memo(function UserAvatar({ onClick = NOOP }: { onClick?: () => void }) {
|
||||||
|
// ...
|
||||||
|
})
|
||||||
|
|
||||||
|
// Used without optional onClick
|
||||||
|
<UserAvatar />
|
||||||
|
```
|
||||||
@@ -0,0 +1,44 @@
|
|||||||
|
---
|
||||||
|
title: Extract to Memoized Components
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: enables early returns
|
||||||
|
tags: rerender, memo, useMemo, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Extract to Memoized Components
|
||||||
|
|
||||||
|
Extract expensive work into memoized components to enable early returns before computation.
|
||||||
|
|
||||||
|
**Incorrect (computes avatar even when loading):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Profile({ user, loading }: Props) {
|
||||||
|
const avatar = useMemo(() => {
|
||||||
|
const id = computeAvatarId(user)
|
||||||
|
return <Avatar id={id} />
|
||||||
|
}, [user])
|
||||||
|
|
||||||
|
if (loading) return <Skeleton />
|
||||||
|
return <div>{avatar}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (skips computation when loading):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
const UserAvatar = memo(function UserAvatar({ user }: { user: User }) {
|
||||||
|
const id = useMemo(() => computeAvatarId(user), [user])
|
||||||
|
return <Avatar id={id} />
|
||||||
|
})
|
||||||
|
|
||||||
|
function Profile({ user, loading }: Props) {
|
||||||
|
if (loading) return <Skeleton />
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<UserAvatar user={user} />
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, manual memoization with `memo()` and `useMemo()` is not necessary. The compiler automatically optimizes re-renders.
|
||||||
@@ -0,0 +1,45 @@
|
|||||||
|
---
|
||||||
|
title: Put Interaction Logic in Event Handlers
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoids effect re-runs and duplicate side effects
|
||||||
|
tags: rerender, useEffect, events, side-effects, dependencies
|
||||||
|
---
|
||||||
|
|
||||||
|
## Put Interaction Logic in Event Handlers
|
||||||
|
|
||||||
|
If a side effect is triggered by a specific user action (submit, click, drag), run it in that event handler. Do not model the action as state + effect; it makes effects re-run on unrelated changes and can duplicate the action.
|
||||||
|
|
||||||
|
**Incorrect (event modeled as state + effect):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Form() {
|
||||||
|
const [submitted, setSubmitted] = useState(false)
|
||||||
|
const theme = useContext(ThemeContext)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
if (submitted) {
|
||||||
|
post('/api/register')
|
||||||
|
showToast('Registered', theme)
|
||||||
|
}
|
||||||
|
}, [submitted, theme])
|
||||||
|
|
||||||
|
return <button onClick={() => setSubmitted(true)}>Submit</button>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (do it in the handler):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Form() {
|
||||||
|
const theme = useContext(ThemeContext)
|
||||||
|
|
||||||
|
function handleSubmit() {
|
||||||
|
post('/api/register')
|
||||||
|
showToast('Registered', theme)
|
||||||
|
}
|
||||||
|
|
||||||
|
return <button onClick={handleSubmit}>Submit</button>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [Should this code move to an event handler?](https://react.dev/learn/removing-effect-dependencies#should-this-code-move-to-an-event-handler)
|
||||||
@@ -0,0 +1,35 @@
|
|||||||
|
---
|
||||||
|
title: Do not wrap a simple expression with a primitive result type in useMemo
|
||||||
|
impact: LOW-MEDIUM
|
||||||
|
impactDescription: wasted computation on every render
|
||||||
|
tags: rerender, useMemo, optimization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Do not wrap a simple expression with a primitive result type in useMemo
|
||||||
|
|
||||||
|
When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`.
|
||||||
|
Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself.
|
||||||
|
|
||||||
|
**Incorrect:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Header({ user, notifications }: Props) {
|
||||||
|
const isLoading = useMemo(() => {
|
||||||
|
return user.isLoading || notifications.isLoading
|
||||||
|
}, [user.isLoading, notifications.isLoading])
|
||||||
|
|
||||||
|
if (isLoading) return <Skeleton />
|
||||||
|
// return some markup
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Header({ user, notifications }: Props) {
|
||||||
|
const isLoading = user.isLoading || notifications.isLoading
|
||||||
|
|
||||||
|
if (isLoading) return <Skeleton />
|
||||||
|
// return some markup
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,40 @@
|
|||||||
|
---
|
||||||
|
title: Use Transitions for Non-Urgent Updates
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: maintains UI responsiveness
|
||||||
|
tags: rerender, transitions, startTransition, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use Transitions for Non-Urgent Updates
|
||||||
|
|
||||||
|
Mark frequent, non-urgent state updates as transitions to maintain UI responsiveness.
|
||||||
|
|
||||||
|
**Incorrect (blocks UI on every scroll):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function ScrollTracker() {
|
||||||
|
const [scrollY, setScrollY] = useState(0)
|
||||||
|
useEffect(() => {
|
||||||
|
const handler = () => setScrollY(window.scrollY)
|
||||||
|
window.addEventListener('scroll', handler, { passive: true })
|
||||||
|
return () => window.removeEventListener('scroll', handler)
|
||||||
|
}, [])
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (non-blocking updates):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { startTransition } from 'react'
|
||||||
|
|
||||||
|
function ScrollTracker() {
|
||||||
|
const [scrollY, setScrollY] = useState(0)
|
||||||
|
useEffect(() => {
|
||||||
|
const handler = () => {
|
||||||
|
startTransition(() => setScrollY(window.scrollY))
|
||||||
|
}
|
||||||
|
window.addEventListener('scroll', handler, { passive: true })
|
||||||
|
return () => window.removeEventListener('scroll', handler)
|
||||||
|
}, [])
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,73 @@
|
|||||||
|
---
|
||||||
|
title: Use useRef for Transient Values
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: avoids unnecessary re-renders on frequent updates
|
||||||
|
tags: rerender, useref, state, performance
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use useRef for Transient Values
|
||||||
|
|
||||||
|
When a value changes frequently and you don't want a re-render on every update (e.g., mouse trackers, intervals, transient flags), store it in `useRef` instead of `useState`. Keep component state for UI; use refs for temporary DOM-adjacent values. Updating a ref does not trigger a re-render.
|
||||||
|
|
||||||
|
**Incorrect (renders every update):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Tracker() {
|
||||||
|
const [lastX, setLastX] = useState(0)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
const onMove = (e: MouseEvent) => setLastX(e.clientX)
|
||||||
|
window.addEventListener('mousemove', onMove)
|
||||||
|
return () => window.removeEventListener('mousemove', onMove)
|
||||||
|
}, [])
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div
|
||||||
|
style={{
|
||||||
|
position: 'fixed',
|
||||||
|
top: 0,
|
||||||
|
left: lastX,
|
||||||
|
width: 8,
|
||||||
|
height: 8,
|
||||||
|
background: 'black',
|
||||||
|
}}
|
||||||
|
/>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (no re-render for tracking):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
function Tracker() {
|
||||||
|
const lastXRef = useRef(0)
|
||||||
|
const dotRef = useRef<HTMLDivElement>(null)
|
||||||
|
|
||||||
|
useEffect(() => {
|
||||||
|
const onMove = (e: MouseEvent) => {
|
||||||
|
lastXRef.current = e.clientX
|
||||||
|
const node = dotRef.current
|
||||||
|
if (node) {
|
||||||
|
node.style.transform = `translateX(${e.clientX}px)`
|
||||||
|
}
|
||||||
|
}
|
||||||
|
window.addEventListener('mousemove', onMove)
|
||||||
|
return () => window.removeEventListener('mousemove', onMove)
|
||||||
|
}, [])
|
||||||
|
|
||||||
|
return (
|
||||||
|
<div
|
||||||
|
ref={dotRef}
|
||||||
|
style={{
|
||||||
|
position: 'fixed',
|
||||||
|
top: 0,
|
||||||
|
left: 0,
|
||||||
|
width: 8,
|
||||||
|
height: 8,
|
||||||
|
background: 'black',
|
||||||
|
transform: 'translateX(0px)',
|
||||||
|
}}
|
||||||
|
/>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,73 @@
|
|||||||
|
---
|
||||||
|
title: Use after() for Non-Blocking Operations
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: faster response times
|
||||||
|
tags: server, async, logging, analytics, side-effects
|
||||||
|
---
|
||||||
|
|
||||||
|
## Use after() for Non-Blocking Operations
|
||||||
|
|
||||||
|
Use Next.js's `after()` to schedule work that should execute after a response is sent. This prevents logging, analytics, and other side effects from blocking the response.
|
||||||
|
|
||||||
|
**Incorrect (blocks response):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { logUserAction } from '@/app/utils'
|
||||||
|
|
||||||
|
export async function POST(request: Request) {
|
||||||
|
// Perform mutation
|
||||||
|
await updateDatabase(request)
|
||||||
|
|
||||||
|
// Logging blocks the response
|
||||||
|
const userAgent = request.headers.get('user-agent') || 'unknown'
|
||||||
|
await logUserAction({ userAgent })
|
||||||
|
|
||||||
|
return new Response(JSON.stringify({ status: 'success' }), {
|
||||||
|
status: 200,
|
||||||
|
headers: { 'Content-Type': 'application/json' }
|
||||||
|
})
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (non-blocking):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
import { after } from 'next/server'
|
||||||
|
import { headers, cookies } from 'next/headers'
|
||||||
|
import { logUserAction } from '@/app/utils'
|
||||||
|
|
||||||
|
export async function POST(request: Request) {
|
||||||
|
// Perform mutation
|
||||||
|
await updateDatabase(request)
|
||||||
|
|
||||||
|
// Log after response is sent
|
||||||
|
after(async () => {
|
||||||
|
const userAgent = (await headers()).get('user-agent') || 'unknown'
|
||||||
|
const sessionCookie = (await cookies()).get('session-id')?.value || 'anonymous'
|
||||||
|
|
||||||
|
logUserAction({ sessionCookie, userAgent })
|
||||||
|
})
|
||||||
|
|
||||||
|
return new Response(JSON.stringify({ status: 'success' }), {
|
||||||
|
status: 200,
|
||||||
|
headers: { 'Content-Type': 'application/json' }
|
||||||
|
})
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
The response is sent immediately while logging happens in the background.
|
||||||
|
|
||||||
|
**Common use cases:**
|
||||||
|
|
||||||
|
- Analytics tracking
|
||||||
|
- Audit logging
|
||||||
|
- Sending notifications
|
||||||
|
- Cache invalidation
|
||||||
|
- Cleanup tasks
|
||||||
|
|
||||||
|
**Important notes:**
|
||||||
|
|
||||||
|
- `after()` runs even if the response fails or redirects
|
||||||
|
- Works in Server Actions, Route Handlers, and Server Components
|
||||||
|
|
||||||
|
Reference: [https://nextjs.org/docs/app/api-reference/functions/after](https://nextjs.org/docs/app/api-reference/functions/after)
|
||||||
@@ -0,0 +1,96 @@
|
|||||||
|
---
|
||||||
|
title: Authenticate Server Actions Like API Routes
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: prevents unauthorized access to server mutations
|
||||||
|
tags: server, server-actions, authentication, security, authorization
|
||||||
|
---
|
||||||
|
|
||||||
|
## Authenticate Server Actions Like API Routes
|
||||||
|
|
||||||
|
**Impact: CRITICAL (prevents unauthorized access to server mutations)**
|
||||||
|
|
||||||
|
Server Actions (functions with `"use server"`) are exposed as public endpoints, just like API routes. Always verify authentication and authorization **inside** each Server Action—do not rely solely on middleware, layout guards, or page-level checks, as Server Actions can be invoked directly.
|
||||||
|
|
||||||
|
Next.js documentation explicitly states: "Treat Server Actions with the same security considerations as public-facing API endpoints, and verify if the user is allowed to perform a mutation."
|
||||||
|
|
||||||
|
**Incorrect (no authentication check):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
'use server'
|
||||||
|
|
||||||
|
export async function deleteUser(userId: string) {
|
||||||
|
// Anyone can call this! No auth check
|
||||||
|
await db.user.delete({ where: { id: userId } })
|
||||||
|
return { success: true }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (authentication inside the action):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
'use server'
|
||||||
|
|
||||||
|
import { verifySession } from '@/lib/auth'
|
||||||
|
import { unauthorized } from '@/lib/errors'
|
||||||
|
|
||||||
|
export async function deleteUser(userId: string) {
|
||||||
|
// Always check auth inside the action
|
||||||
|
const session = await verifySession()
|
||||||
|
|
||||||
|
if (!session) {
|
||||||
|
throw unauthorized('Must be logged in')
|
||||||
|
}
|
||||||
|
|
||||||
|
// Check authorization too
|
||||||
|
if (session.user.role !== 'admin' && session.user.id !== userId) {
|
||||||
|
throw unauthorized('Cannot delete other users')
|
||||||
|
}
|
||||||
|
|
||||||
|
await db.user.delete({ where: { id: userId } })
|
||||||
|
return { success: true }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**With input validation:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
'use server'
|
||||||
|
|
||||||
|
import { verifySession } from '@/lib/auth'
|
||||||
|
import { z } from 'zod'
|
||||||
|
|
||||||
|
const updateProfileSchema = z.object({
|
||||||
|
userId: z.string().uuid(),
|
||||||
|
name: z.string().min(1).max(100),
|
||||||
|
email: z.string().email()
|
||||||
|
})
|
||||||
|
|
||||||
|
export async function updateProfile(data: unknown) {
|
||||||
|
// Validate input first
|
||||||
|
const validated = updateProfileSchema.parse(data)
|
||||||
|
|
||||||
|
// Then authenticate
|
||||||
|
const session = await verifySession()
|
||||||
|
if (!session) {
|
||||||
|
throw new Error('Unauthorized')
|
||||||
|
}
|
||||||
|
|
||||||
|
// Then authorize
|
||||||
|
if (session.user.id !== validated.userId) {
|
||||||
|
throw new Error('Can only update own profile')
|
||||||
|
}
|
||||||
|
|
||||||
|
// Finally perform the mutation
|
||||||
|
await db.user.update({
|
||||||
|
where: { id: validated.userId },
|
||||||
|
data: {
|
||||||
|
name: validated.name,
|
||||||
|
email: validated.email
|
||||||
|
}
|
||||||
|
})
|
||||||
|
|
||||||
|
return { success: true }
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
Reference: [https://nextjs.org/docs/app/guides/authentication](https://nextjs.org/docs/app/guides/authentication)
|
||||||
@@ -0,0 +1,41 @@
|
|||||||
|
---
|
||||||
|
title: Cross-Request LRU Caching
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: caches across requests
|
||||||
|
tags: server, cache, lru, cross-request
|
||||||
|
---
|
||||||
|
|
||||||
|
## Cross-Request LRU Caching
|
||||||
|
|
||||||
|
`React.cache()` only works within one request. For data shared across sequential requests (user clicks button A then button B), use an LRU cache.
|
||||||
|
|
||||||
|
**Implementation:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
import { LRUCache } from 'lru-cache'
|
||||||
|
|
||||||
|
const cache = new LRUCache<string, any>({
|
||||||
|
max: 1000,
|
||||||
|
ttl: 5 * 60 * 1000 // 5 minutes
|
||||||
|
})
|
||||||
|
|
||||||
|
export async function getUser(id: string) {
|
||||||
|
const cached = cache.get(id)
|
||||||
|
if (cached) return cached
|
||||||
|
|
||||||
|
const user = await db.user.findUnique({ where: { id } })
|
||||||
|
cache.set(id, user)
|
||||||
|
return user
|
||||||
|
}
|
||||||
|
|
||||||
|
// Request 1: DB query, result cached
|
||||||
|
// Request 2: cache hit, no DB query
|
||||||
|
```
|
||||||
|
|
||||||
|
Use when sequential user actions hit multiple endpoints needing the same data within seconds.
|
||||||
|
|
||||||
|
**With Vercel's [Fluid Compute](https://vercel.com/docs/fluid-compute):** LRU caching is especially effective because multiple concurrent requests can share the same function instance and cache. This means the cache persists across requests without needing external storage like Redis.
|
||||||
|
|
||||||
|
**In traditional serverless:** Each invocation runs in isolation, so consider Redis for cross-process caching.
|
||||||
|
|
||||||
|
Reference: [https://github.com/isaacs/node-lru-cache](https://github.com/isaacs/node-lru-cache)
|
||||||
@@ -0,0 +1,76 @@
|
|||||||
|
---
|
||||||
|
title: Per-Request Deduplication with React.cache()
|
||||||
|
impact: MEDIUM
|
||||||
|
impactDescription: deduplicates within request
|
||||||
|
tags: server, cache, react-cache, deduplication
|
||||||
|
---
|
||||||
|
|
||||||
|
## Per-Request Deduplication with React.cache()
|
||||||
|
|
||||||
|
Use `React.cache()` for server-side request deduplication. Authentication and database queries benefit most.
|
||||||
|
|
||||||
|
**Usage:**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
import { cache } from 'react'
|
||||||
|
|
||||||
|
export const getCurrentUser = cache(async () => {
|
||||||
|
const session = await auth()
|
||||||
|
if (!session?.user?.id) return null
|
||||||
|
return await db.user.findUnique({
|
||||||
|
where: { id: session.user.id }
|
||||||
|
})
|
||||||
|
})
|
||||||
|
```
|
||||||
|
|
||||||
|
Within a single request, multiple calls to `getCurrentUser()` execute the query only once.
|
||||||
|
|
||||||
|
**Avoid inline objects as arguments:**
|
||||||
|
|
||||||
|
`React.cache()` uses shallow equality (`Object.is`) to determine cache hits. Inline objects create new references each call, preventing cache hits.
|
||||||
|
|
||||||
|
**Incorrect (always cache miss):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const getUser = cache(async (params: { uid: number }) => {
|
||||||
|
return await db.user.findUnique({ where: { id: params.uid } })
|
||||||
|
})
|
||||||
|
|
||||||
|
// Each call creates new object, never hits cache
|
||||||
|
getUser({ uid: 1 })
|
||||||
|
getUser({ uid: 1 }) // Cache miss, runs query again
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (cache hit):**
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const getUser = cache(async (uid: number) => {
|
||||||
|
return await db.user.findUnique({ where: { id: uid } })
|
||||||
|
})
|
||||||
|
|
||||||
|
// Primitive args use value equality
|
||||||
|
getUser(1)
|
||||||
|
getUser(1) // Cache hit, returns cached result
|
||||||
|
```
|
||||||
|
|
||||||
|
If you must pass objects, pass the same reference:
|
||||||
|
|
||||||
|
```typescript
|
||||||
|
const params = { uid: 1 }
|
||||||
|
getUser(params) // Query runs
|
||||||
|
getUser(params) // Cache hit (same reference)
|
||||||
|
```
|
||||||
|
|
||||||
|
**Next.js-Specific Note:**
|
||||||
|
|
||||||
|
In Next.js, the `fetch` API is automatically extended with request memoization. Requests with the same URL and options are automatically deduplicated within a single request, so you don't need `React.cache()` for `fetch` calls. However, `React.cache()` is still essential for other async tasks:
|
||||||
|
|
||||||
|
- Database queries (Prisma, Drizzle, etc.)
|
||||||
|
- Heavy computations
|
||||||
|
- Authentication checks
|
||||||
|
- File system operations
|
||||||
|
- Any non-fetch async work
|
||||||
|
|
||||||
|
Use `React.cache()` to deduplicate these operations across your component tree.
|
||||||
|
|
||||||
|
Reference: [React.cache documentation](https://react.dev/reference/react/cache)
|
||||||
@@ -0,0 +1,65 @@
|
|||||||
|
---
|
||||||
|
title: Avoid Duplicate Serialization in RSC Props
|
||||||
|
impact: LOW
|
||||||
|
impactDescription: reduces network payload by avoiding duplicate serialization
|
||||||
|
tags: server, rsc, serialization, props, client-components
|
||||||
|
---
|
||||||
|
|
||||||
|
## Avoid Duplicate Serialization in RSC Props
|
||||||
|
|
||||||
|
**Impact: LOW (reduces network payload by avoiding duplicate serialization)**
|
||||||
|
|
||||||
|
RSC→client serialization deduplicates by object reference, not value. Same reference = serialized once; new reference = serialized again. Do transformations (`.toSorted()`, `.filter()`, `.map()`) in client, not server.
|
||||||
|
|
||||||
|
**Incorrect (duplicates array):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
// RSC: sends 6 strings (2 arrays × 3 items)
|
||||||
|
<ClientList usernames={usernames} usernamesOrdered={usernames.toSorted()} />
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (sends 3 strings):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
// RSC: send once
|
||||||
|
<ClientList usernames={usernames} />
|
||||||
|
|
||||||
|
// Client: transform there
|
||||||
|
'use client'
|
||||||
|
const sorted = useMemo(() => [...usernames].sort(), [usernames])
|
||||||
|
```
|
||||||
|
|
||||||
|
**Nested deduplication behavior:**
|
||||||
|
|
||||||
|
Deduplication works recursively. Impact varies by data type:
|
||||||
|
|
||||||
|
- `string[]`, `number[]`, `boolean[]`: **HIGH impact** - array + all primitives fully duplicated
|
||||||
|
- `object[]`: **LOW impact** - array duplicated, but nested objects deduplicated by reference
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
// string[] - duplicates everything
|
||||||
|
usernames={['a','b']} sorted={usernames.toSorted()} // sends 4 strings
|
||||||
|
|
||||||
|
// object[] - duplicates array structure only
|
||||||
|
users={[{id:1},{id:2}]} sorted={users.toSorted()} // sends 2 arrays + 2 unique objects (not 4)
|
||||||
|
```
|
||||||
|
|
||||||
|
**Operations breaking deduplication (create new references):**
|
||||||
|
|
||||||
|
- Arrays: `.toSorted()`, `.filter()`, `.map()`, `.slice()`, `[...arr]`
|
||||||
|
- Objects: `{...obj}`, `Object.assign()`, `structuredClone()`, `JSON.parse(JSON.stringify())`
|
||||||
|
|
||||||
|
**More examples:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
// ❌ Bad
|
||||||
|
<C users={users} active={users.filter(u => u.active)} />
|
||||||
|
<C product={product} productName={product.name} />
|
||||||
|
|
||||||
|
// ✅ Good
|
||||||
|
<C users={users} />
|
||||||
|
<C product={product} />
|
||||||
|
// Do filtering/destructuring in client
|
||||||
|
```
|
||||||
|
|
||||||
|
**Exception:** Pass derived data when transformation is expensive or client doesn't need original.
|
||||||
@@ -0,0 +1,83 @@
|
|||||||
|
---
|
||||||
|
title: Parallel Data Fetching with Component Composition
|
||||||
|
impact: CRITICAL
|
||||||
|
impactDescription: eliminates server-side waterfalls
|
||||||
|
tags: server, rsc, parallel-fetching, composition
|
||||||
|
---
|
||||||
|
|
||||||
|
## Parallel Data Fetching with Component Composition
|
||||||
|
|
||||||
|
React Server Components execute sequentially within a tree. Restructure with composition to parallelize data fetching.
|
||||||
|
|
||||||
|
**Incorrect (Sidebar waits for Page's fetch to complete):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
export default async function Page() {
|
||||||
|
const header = await fetchHeader()
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<div>{header}</div>
|
||||||
|
<Sidebar />
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
async function Sidebar() {
|
||||||
|
const items = await fetchSidebarItems()
|
||||||
|
return <nav>{items.map(renderItem)}</nav>
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (both fetch simultaneously):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
async function Header() {
|
||||||
|
const data = await fetchHeader()
|
||||||
|
return <div>{data}</div>
|
||||||
|
}
|
||||||
|
|
||||||
|
async function Sidebar() {
|
||||||
|
const items = await fetchSidebarItems()
|
||||||
|
return <nav>{items.map(renderItem)}</nav>
|
||||||
|
}
|
||||||
|
|
||||||
|
export default function Page() {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<Header />
|
||||||
|
<Sidebar />
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Alternative with children prop:**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
async function Header() {
|
||||||
|
const data = await fetchHeader()
|
||||||
|
return <div>{data}</div>
|
||||||
|
}
|
||||||
|
|
||||||
|
async function Sidebar() {
|
||||||
|
const items = await fetchSidebarItems()
|
||||||
|
return <nav>{items.map(renderItem)}</nav>
|
||||||
|
}
|
||||||
|
|
||||||
|
function Layout({ children }: { children: ReactNode }) {
|
||||||
|
return (
|
||||||
|
<div>
|
||||||
|
<Header />
|
||||||
|
{children}
|
||||||
|
</div>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
|
||||||
|
export default function Page() {
|
||||||
|
return (
|
||||||
|
<Layout>
|
||||||
|
<Sidebar />
|
||||||
|
</Layout>
|
||||||
|
)
|
||||||
|
}
|
||||||
|
```
|
||||||
@@ -0,0 +1,38 @@
|
|||||||
|
---
|
||||||
|
title: Minimize Serialization at RSC Boundaries
|
||||||
|
impact: HIGH
|
||||||
|
impactDescription: reduces data transfer size
|
||||||
|
tags: server, rsc, serialization, props
|
||||||
|
---
|
||||||
|
|
||||||
|
## Minimize Serialization at RSC Boundaries
|
||||||
|
|
||||||
|
The React Server/Client boundary serializes all object properties into strings and embeds them in the HTML response and subsequent RSC requests. This serialized data directly impacts page weight and load time, so **size matters a lot**. Only pass fields that the client actually uses.
|
||||||
|
|
||||||
|
**Incorrect (serializes all 50 fields):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
async function Page() {
|
||||||
|
const user = await fetchUser() // 50 fields
|
||||||
|
return <Profile user={user} />
|
||||||
|
}
|
||||||
|
|
||||||
|
'use client'
|
||||||
|
function Profile({ user }: { user: User }) {
|
||||||
|
return <div>{user.name}</div> // uses 1 field
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Correct (serializes only 1 field):**
|
||||||
|
|
||||||
|
```tsx
|
||||||
|
async function Page() {
|
||||||
|
const user = await fetchUser()
|
||||||
|
return <Profile name={user.name} />
|
||||||
|
}
|
||||||
|
|
||||||
|
'use client'
|
||||||
|
function Profile({ name }: { name: string }) {
|
||||||
|
return <div>{name}</div>
|
||||||
|
}
|
||||||
|
```
|
||||||
0
profiles/opencode/tool/.gitkeep
Normal file
0
profiles/opencode/tool/.gitkeep
Normal file
Reference in New Issue
Block a user