Flatten an array of arbitrarily nested arrays of values into a flat array of values. e.g. [[1,2,[3]],4] -> [1,2,3,4].

README.md

flattenArray

Flatten an array of arbitrarily nested arrays of values into a flat array of values

Usage

// Both CommonJS and ES6 import syntaxes are supported
// import flattenArray from './flattenArray'
const flattenArray = require('./flattenArray')

flattenArray([[1,2,[3]],4]) // [1, 2, 3 , 4]

Test

Launch

node flattenArray.test.js

License

MIT

_{Latest sources here: https://gist.github.com/fibo/0ec16d96b16719a045fd561cd74a12c8}

flattenArray.js

/**
 * flattenArray
 * @function
 *
 * Flatten an array of arbitrarily nested arrays of values into a flat array of values. e.g. [[1,2,[3]],4] -> [1,2,3,4].
 *
 * example usage:
 *
 * flattenArray([[1,2,[3]],4]) // [1, 2, 3 , 4]
 *
 * @param {Array} input
 * @returns {Array} output
 *
 * License: MIT
 * Author: Gianluca Casati a.k.a. fibo, http://g14n.info
 * Sources here: https://gist.github.com/fibo/0ec16d96b16719a045fd561cd74a12c8
 */

function flattenArray (input) {
  // Check that input is an array, if yes, flatten it with a recursive reducer.
  if (Array.isArray(input)) {
    return input.reduce(
      function flattener (accumulator, value) {
        if (Array.isArray(value)) {
          // If array item is an array, flatten it recursively...
          return accumulator.concat(value.reduce(flattener, []))
        } else {
          // ...otherwise append it to result array.
          return accumulator.concat(value)
        }
      }
      , []
    )
  } else {
    throw new TypeError('Argument must be an array')
  }
}

// CommonJS / ES6 export
module.exports = exports.default = flattenArray

flattenArray.test.js

// To run this test, launch
//
// node flattenArray.test.js
const assert = require('assert')

const flattenArray = require('./flattenArray')

const tests = [
  {
    input: [[1,2,[3]],4],
    output: [1, 2, 3, 4]
  },
  {
    input: [],
    output: []
  },
  {
    input: ['a', 'b'],
    output: ['a', 'b']
  },
  {
    input: [1, [2, [3, [4, 5, [6, 7], 8], 9], 10, 11], 12],
    output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
  }
]


tests.forEach(({ input, output }) => {
  assert.deepEqual(flattenArray(input), output)
})

console.log(`run ${tests.length} tests`)