js-set-map-lookups
Use Set and Map for O(1) membership lookups instead of array.includes(). Apply when checking membership repeatedly or performing frequent lookups against a collection.
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- TheOrcDev/8bitcn-ui
- Last source activity
- January 16, 2026 at 09:09
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- English
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- 2,043
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- js-set-map-lookups
- description
- Use Set and Map for O(1) membership lookups instead of array.includes(). Apply when checking membership repeatedly or performing frequent lookups against a collection.
## Use Set/Map for O(1) Lookups
Convert arrays to Set/Map for repeated membership checks.
**Incorrect (O(n) per check):**
```typescript
const allowedIds = ['a', 'b', 'c', ...]
items.filter(item => allowedIds.includes(item.id))
```
**Correct (O(1) per check):**
```typescript
const allowedIds = new Set(['a', 'b', 'c', ...])
items.filter(item => allowedIds.has(item.id))
```
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