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- Added new skills: find-skills, frontend-ui-engineering, and vercel-react-best-practices to skills-lock.json. - Updated use-pixel-heat.ts to import both animate and AnimationPlaybackControls from motion for improved animation handling.
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title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Hoist RegExp Creation | LOW-MEDIUM | avoids recreation | 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):
function Highlighter({ text, query }: Props) {
const regex = new RegExp(`(${query})`, 'gi')
const parts = text.split(regex)
return <>{parts.map((part, i) => ...)}</>
}
Correct (memoize or hoist):
const EMAIL_REGEX = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
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:
const regex = /foo/g
regex.test('foo') // true, lastIndex = 3
regex.test('foo') // false, lastIndex = 0