dcaaef1011
Format: YYYY-MM-DD-description.md - 2026-01-19-infrastructure-deployment.md - 2026-01-19-backend-api-implementation.md (in progress) Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>
1.0 KiB
1.0 KiB
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