prefer-flat

Use .flat() to flatten an array of arrays. This rule currently recognizes two patterns and can replace them with a .flat() call:

• [].concat(...array)
• array.reduce((p, n) => p.concat(n), [])

This rule is auto fixable.

Examples

Code that triggers this rule:

const concatFlat = [].concat(...array);

const reduceFlat = array.reduce((p, n) => p.concat(n), []);

Code that doesn't trigger this rule:

const flattened = array.flat();

const reverseFlat = array.reduce((p, n) => n.concat(p), []);

const otherReduce = array.reduce((p, n) => n + p, 0);

Using the rule

To use this rule, your eslint.config.js should at least contain the following:

import arrayFunc from "eslint-plugin-array-func";

export default [
  {
    plugins: {
      "array-func": arrayFunc
    },
    rules: {
      "array-func/prefer-flat": "error"
    }
  }
];