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

array-flat.js

/**
 * Array Flat
 * This a commonJS module written in ES6 that will flatten 
 * an array of arbitrarily nested arrays of
 * integers into a flat array of integers.
 * 
 * @example
 *  import arrayFlat from '/your/path/array-flat'
 * 
 *  flatten([0, 1, 3, [4, 5, 6, [4, 6]]])
 *  // -> [0, 1, 3, 4, 5, 6, 4, 6]
 * 
 * @param Array 
 */

const flat = (item, accum) => {
  if (Array.isArray(item)) {
    if (item.length === 0) {
      return accum
    }

    item.forEach(i => flat(i, accum))
    return accum;
  } else {
    accum.push(item)
    return accum
  }
}

function flatten (arr) {
  if (!Array.isArray(arr)) return []

  const output = flat(arr, [])

  return output
}

export default flatten