js-combine-iterations

Multiple .filter() or .map() calls iterate the array multiple times. Combine into one loop.

Skills
Web development
1

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mkdir -p .claude/skills/js-combine-iterations && curl -fsSL https://doutorai.pt/data/lib/skills__js-combine-iterations.md -o .claude/skills/js-combine-iterations/SKILL.md

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Content

---
title: Combine Multiple Array Iterations
impact: LOW-MEDIUM
impactDescription: reduces iterations
tags: javascript, arrays, loops, performance
---

## Combine Multiple Array Iterations

Multiple `.filter()` or `.map()` calls iterate the array multiple times. Combine into one loop.

**Incorrect (3 iterations):**

```typescript
const admins = users.filter(u => u.isAdmin)
const testers = users.filter(u => u.isTester)
const inactive = users.filter(u => !u.isActive)
```

**Correct (1 iteration):**

```typescript
const admins: User[] = []
const testers: User[] = []
const inactive: User[] = []

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