[ PROMPT_NODE_27947 ]
Js Hoist Regexp
[ SKILL_DOCUMENTATION ]
## Hoist RegExp Creation
Don't create RegExp inside render. Hoist to module scope or memoize with `useMemo()`.
**Incorrect (new RegExp every render):**
```tsx
function Highlighter({ text, query }: Props) {
const regex = new RegExp(`(${query})`, 'gi')
const parts = text.split(regex)
return {parts.map((part, i) => ...)} new RegExp(`(${escapeRegex(query)})`, 'gi'),
[query]
)
const parts = text.split(regex)
return {parts.map((part, i) => ...)}
}
```
**Warning:** Global regex (`/g`) has mutable `lastIndex` state:
```typescript
const regex = /foo/g
regex.test('foo') // true, lastIndex = 3
regex.test('foo') // false, lastIndex = 0
```