d9bcdc4a8d
Skills included: - pr-reviewer: Adapted for Gitea/GitHub via platform-aware scripts (dropped fetch_pr_data.py and add_inline_comment.py, kept generate_review_files.py) - code-review-excellence: Methodology and checklists (React, TS, Python, etc.) - vercel-react-best-practices: 57 rules for React/Next.js performance - tailwind-design-system: Tailwind CSS v4 patterns, CVA, design tokens New shell scripts added to ~/.claude/scripts/git/: - pr-diff.sh: Get PR diff (GitHub gh / Gitea API) - pr-metadata.sh: Get PR metadata as normalized JSON Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2.0 KiB
2.0 KiB
title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Use Lazy State Initialization | MEDIUM | wasted computation on every render | 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):
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):
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.