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33 lines
753 B
Markdown
33 lines
753 B
Markdown
---
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title: Combine Multiple Array Iterations
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impact: LOW-MEDIUM
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impactDescription: reduces iterations
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tags: javascript, arrays, loops, performance
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---
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## Combine Multiple Array Iterations
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Multiple `.filter()` or `.map()` calls iterate the array multiple times. Combine into one loop.
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**Incorrect (3 iterations):**
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```typescript
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const admins = users.filter(u => u.isAdmin)
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const testers = users.filter(u => u.isTester)
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const inactive = users.filter(u => !u.isActive)
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```
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**Correct (1 iteration):**
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```typescript
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const admins: User[] = []
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const testers: User[] = []
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const inactive: User[] = []
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for (const user of users) {
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if (user.isAdmin) admins.push(user)
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if (user.isTester) testers.push(user)
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if (!user.isActive) inactive.push(user)
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}
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```
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