index.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = global || self, global.arrayBack = factory());
}(this, function () { 'use strict';

  /**
   * Takes any input and guarantees an array back.
   *
   * - Converts array-like objects (e.g. `arguments`, `Set`) to a real array.
   * - Converts `undefined` to an empty array.
   * - Converts any another other, singular value (including `null`, objects and iterables other than `Set`) into an array containing that value.
   * - Ignores input which is already an array.
   *
   * @module array-back
   * @example
   * > const arrayify = require('array-back')
   *
   * > arrayify(undefined)
   * []
   *
   * > arrayify(null)
   * [ null ]
   *
   * > arrayify(0)
   * [ 0 ]
   *
   * > arrayify([ 1, 2 ])
   * [ 1, 2 ]
   *
   * > arrayify(new Set([ 1, 2 ]))
   * [ 1, 2 ]
   *
   * > function f(){ return arrayify(arguments); }
   * > f(1,2,3)
   * [ 1, 2, 3 ]
   */

  function isObject (input) {
    return typeof input === 'object' && input !== null
  }

  function isArrayLike (input) {
    return isObject(input) && typeof input.length === 'number'
  }

  /**
   * @param {*} - The input value to convert to an array
   * @returns {Array}
   * @alias module:array-back
   */
  function arrayify (input) {
    if (Array.isArray(input)) {
      return input
    }

    if (input === undefined) {
      return []
    }

    if (isArrayLike(input) || input instanceof Set) {
      return Array.from(input)
    }

    return [ input ]
  }

  return arrayify;

}));