React Best Practices (Desktop/Client Edition)

Performance optimization guide tailored for client-rendered React applications: Electron desktop apps, Vite SPAs, and any React app without SSR. Adapted from Vercel Engineering's original guide. Contains 57 rules across 7 categories.

When to Apply

Reference these guidelines when:

• Writing new React components or hooks
• Implementing data loading (IPC calls, file reads, async operations)
• Reviewing code for performance issues
• Refactoring existing React code
• Optimizing bundle size or startup time
• Reducing unnecessary re-renders

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Eliminating Waterfalls	CRITICAL	async-
2	Bundle Size Optimization	CRITICAL	bundle-
3	Client-Side Data Fetching	MEDIUM	client-
4	Re-render Optimization	MEDIUM	rerender-
5	Rendering Performance	MEDIUM	rendering-
6	JavaScript Performance	LOW-MEDIUM	js-
7	Advanced Patterns	LOW	advanced-

Quick Reference

1. Eliminating Waterfalls (CRITICAL)

• async-cheap-condition-before-await - Check cheap sync conditions before async work
• async-defer-await - Move await into branches where actually used
• async-parallel - Use Promise.all() for independent operations
• async-dependencies - Chain promises for partial dependencies
• async-api-routes - Start promises early, await late
• async-suspense-boundaries - Use Suspense for faster initial render
• async-parallel-nested - Chain nested async operations per item in Promise.all

2. Bundle Size Optimization (CRITICAL)

• bundle-barrel-imports - Import directly, avoid barrel files
• bundle-analyzable-paths - Prefer statically analyzable import paths
• bundle-dynamic-imports - Use React.lazy() for heavy components
• bundle-defer-third-party - Load analytics/logging after initial render
• bundle-conditional - Load modules only when feature is activated
• bundle-preload - Preload on hover/focus for perceived speed

3. Client-Side Data Patterns (MEDIUM)

• client-event-listeners - Deduplicate global event listeners with module-level Map
• client-passive-event-listeners - Use passive listeners for scroll
• client-localstorage-schema - Version and minimize localStorage data

4. Re-render Optimization (MEDIUM)

• rerender-defer-reads - Use getState() for values only needed 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-split-combined-hooks - Split hooks with independent dependencies
• rerender-move-effect-to-event - Put interaction logic in event handlers
• rerender-transitions - Use startTransition for non-urgent updates
• rerender-use-deferred-value - Defer expensive renders to keep UI responsive
• rerender-use-ref-transient-values - Use refs for transient frequent values
• rerender-no-inline-components - Don't define components inside components

5. 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-activity - Use Activity component for show/hide
• rendering-conditional-render - Use ternary, not && for conditional rendering
• rendering-usetransition-loading - Prefer useTransition for loading state

6. 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/renders
• 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
• js-flatmap-filter - Use flatMap to map and filter in one pass
• js-request-idle-callback - Defer non-critical work to browser idle time
• js-hoist-static-io - Hoist static file I/O to module level

7. Advanced Patterns (LOW)

• advanced-effect-event-deps - Don't put useEffectEvent results in effect deps
• advanced-event-handler-refs - Store event handlers in refs for stable subscriptions
• advanced-init-once - Initialize app once per app load (module-level guard)
• advanced-use-latest - useEffectEvent for stable callback refs

How to Use

Read individual rule files for detailed explanations and code examples:

rules/async-parallel.md
rules/rerender-memo.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