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Rslint

    no-sparse-arrays

    Configuration

    PresetConfigured Value
    ✅ js.configs.recommended"error"
    ✅ ts.configs.recommended"error"
    rslint.config.ts
    import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-sparse-arrays': 'error',
    },
  },
]);

    Rule Details

    Disallows sparse arrays, which are array literals that contain empty slots created by extra commas. Sparse arrays can be confusing because the empty slots are undefined but behave differently from explicitly setting an element to undefined (for example, Array.prototype.forEach skips sparse entries). Extra commas are usually a typo.

    Examples of incorrect code for this rule:

    var items = [1, , 3];

var colors = ['red', , 'blue'];

    Examples of correct code for this rule:

    var items = [1, 2, 3];

var colors = ['red', 'blue'];

var arr = [1, undefined, 3]; // explicit undefined is fine

    Original Documentation