Agent skill
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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npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/js-set-map-lookups
SKILL.md
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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