type/no-for-in-array

Disallow for-in iteration over array-like values.

Applies to: Type information in Vue SFC scripts and templates, for the constructs shown below.

This rule reads type information from your TypeScript project (tsconfig.json), so the configuration sets typeAware: true. typeAware does not turn on opt-in rules by itself.

Bad

for-in walks the keys of an array instead of its element values.

<script setup lang="ts">
const numbers = [1, 2, 3];
function loopsKeys(): void {
  for (const key in numbers) {
    console.log(key);
  }
}
</script>

Good

for-of walks the numeric elements of the array.

<script setup lang="ts">
const numbers = [1, 2, 3];
function loopsKeys(): void {
  for (const n of numbers) {
    console.log(n);
  }
}
</script>

Configuration (Vite+)

import { defineConfig } from "@vizejs/vite-plugin/vite-plus";

export default defineConfig({}).withVue({
  linter: {
    "preset": "incremental",
    "rules": {
      "type/no-for-in-array": "warn"
    },
    "typeAware": true
  },
});

Then run vp run lint.

Related

• Type and script rules
• All rules
• Source code