The Array.from() method creates a new Array instance from an array-like or iterable object.

// ["f", "o", "o"]


Array.from(arrayLike[, mapFn[, thisArg]])


An array-like or iterable object to convert to an array.
Optional. Map function to call on every element of the array.
Optional. Value to use as this when executing mapFn.

Return value

A new Array instance.


Array.from() lets you create Arrays from:

  • array-like objects (objects with a length property and indexed elements) or
  • iterable objects (objects where you can get its elements, such as Map and Set).

Array.from() has an optional parameter mapFn, which allows you to execute a map function on each element of the array (or subclass object) that is being created. More clearly, Array.from(obj, mapFn, thisArg) has the same result as Array.from(obj).map(mapFn, thisArg), except that it does not create an intermediate array. This is especially important for certain array subclasses, like typed arrays, since the intermediate array would necessarily have values truncated to fit into the appropriate type.

The length property of the from() method is 1.

In ES2015, the class syntax allows for sub-classing of both built-in and user defined classes; as a result, static methods such as Array.from are "inherited" by subclasses of Array and create new instances of the subclass, not Array.


Array from a String

// ["f", "o", "o"]

Array from a Set

var s = new Set(["foo", window]); 
// ["foo", window]

Array from a Map

var m = new Map([[1, 2], [2, 4], [4, 8]]);
// [[1, 2], [2, 4], [4, 8]]

Array from an Array-like object (arguments)

function f() {
  return Array.from(arguments);

f(1, 2, 3);

// [1, 2, 3]

Using arrow functions and Array.from

// Using an arrow function as the map function to
// manipulate the elements
Array.from([1, 2, 3], x => x + x);      
// [2, 4, 6]

// Generate a sequence of numbers
// Since the array is initialized with `undefined` on each position,
// the value of `v` below will be `undefined`
Array.from({length: 5}, (v, i) => i);
// [0, 1, 2, 3, 4]


Array.from was added to the ECMA-262 standard in the 6th edition (ES2015); as such it may not be present in other implementations of the standard. You can work around this by inserting the following code at the beginning of your scripts, allowing use of Array.from in implementations that don't natively support it.  This algorithm is exactly the one specified in ECMA-262, 6th edition, assuming Object and TypeError have their original values and that evaluates to the original value of In addition, since true iterables can not be polyfilled, this implementation does not support generic iterables as defined in the 6th edition of ECMA-262.

// Production steps of ECMA-262, Edition 6,
if (!Array.from) {
  Array.from = (function () {
    var toStr = Object.prototype.toString;
    var isCallable = function (fn) {
      return typeof fn === 'function' || === '[object Function]';
    var toInteger = function (value) {
      var number = Number(value);
      if (isNaN(number)) { return 0; }
      if (number === 0 || !isFinite(number)) { return number; }
      return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
    var maxSafeInteger = Math.pow(2, 53) - 1;
    var toLength = function (value) {
      var len = toInteger(value);
      return Math.min(Math.max(len, 0), maxSafeInteger);

    // The length property of the from method is 1.
    return function from(arrayLike/*, mapFn, thisArg */) {
      // 1. Let C be the this value.
      var C = this;

      // 2. Let items be ToObject(arrayLike).
      var items = Object(arrayLike);

      // 3. ReturnIfAbrupt(items).
      if (arrayLike == null) {
        throw new TypeError("Array.from requires an array-like object - not null or undefined");

      // 4. If mapfn is undefined, then let mapping be false.
      var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
      var T;
      if (typeof mapFn !== 'undefined') {
        // 5. else
        // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
        if (!isCallable(mapFn)) {
          throw new TypeError('Array.from: when provided, the second argument must be a function');

        // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
        if (arguments.length > 2) {
          T = arguments[2];

      // 10. Let lenValue be Get(items, "length").
      // 11. Let len be ToLength(lenValue).
      var len = toLength(items.length);

      // 13. If IsConstructor(C) is true, then
      // 13. a. Let A be the result of calling the [[Construct]] internal method 
      // of C with an argument list containing the single item len.
      // 14. a. Else, Let A be ArrayCreate(len).
      var A = isCallable(C) ? Object(new C(len)) : new Array(len);

      // 16. Let k be 0.
      var k = 0;
      // 17. Repeat, while k < len… (also steps a - h)
      var kValue;
      while (k < len) {
        kValue = items[k];
        if (mapFn) {
          A[k] = typeof T === 'undefined' ? mapFn(kValue, k) :, kValue, k);
        } else {
          A[k] = kValue;
        k += 1;
      // 18. Let putStatus be Put(A, "length", len, true).
      A.length = len;
      // 20. Return A.
      return A;


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.from' in that specification.
Standard Initial definition.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'Array.from' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Edge Internet Explorer Opera Safari
Basic support 45 32 (32) (Yes) No support (Yes) 9.0
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 32.0 (32) No support No support No support

See also

Document Tags and Contributors

 Last updated by: RussVanBert,