React Best Practices

Overview

Comprehensive performance optimization guide for React applications, containing 12 rules across 6 categories. Rules are prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when:

• Writing new React components
• Implementing data fetching
• Reviewing code for performance issues
• Refactoring existing React code
• Optimizing bundle size or load times

Priority-Ordered Guidelines

Rules are prioritized by impact:

Priority	Category	Impact
1	Eliminating Waterfalls	CRITICAL
2	Bundle Size Optimization	CRITICAL
3	Client-Side Data Fetching	MEDIUM-HIGH
4	Re-render Optimization	MEDIUM
5	Rendering Performance	MEDIUM
6	JavaScript Performance	LOW-MEDIUM

Quick Reference

Critical Patterns (Apply First)

Eliminate Waterfalls:

• Use Promise.all() for independent async operations (async-parallel)

Reduce Bundle Size:

• Avoid barrel file imports, import directly from source (bundle-barrel-imports)
• Defer non-critical third-party libraries (bundle-defer-third-party)

Medium-Impact Patterns

Client-Side Data Fetching:

• Use Tanstack Query for automatic request deduplication (client-request-dedupe)

Re-render Optimization:

• Use lazy state initialization for expensive values (rerender-lazy-state-init)
• Apply startTransition for non-urgent updates (rerender-transitions)
• Minimize useEffect function calls (rerender-useeffect-function-calls)

Rendering Patterns

• Animate SVG wrappers, not SVG elements directly (rendering-animate-svg-wrapper)
• Use content-visibility: auto for long lists (rendering-content-visibility)

JavaScript Patterns

• Use Set/Map for repeated lookups (js-set-map-lookups)
• Use toSorted() instead of sort() for immutability (js-tosorted-immutable)
• Early length check for array comparisons (js-length-check-first)

References

Full documentation with code examples is available in:

• references/react-best-practices-reference.md - Complete guide with all patterns
• references/rules/ - Individual rule files organized by category

To look up a specific pattern, grep the rules directory:

grep -l "Promise.all" references/rules/
grep -l "barrel" references/rules/
grep -l "Tanstack" references/rules/

Rule Categories in references/rules/

• async-* - Waterfall elimination (1 rule)
• bundle-* - Bundle size optimization (2 rules)
• client-* - Client-side data fetching (1 rule)
• rerender-* - Re-render optimization (3 rules)
• rendering-* - DOM rendering performance (2 rules)
• js-* - JavaScript micro-optimizations (3 rules)