Js Combine Iterations

---
name: js-combine-iterations
description: Combine Multiple Array Iterations. Use when you need help with js combine iterations.
license: CC-BY-NC-SA-4.0
metadata:
  risk: unknown
  source: community
  kind: mode
  category: rules
---

## 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[] = [];

for (const user of users) {
  if (user.isAdmin) admins.push(user);
  if (user.isTester) testers.push(user);
  if (!user.isActive) inactive.push(user);
}
```