path: root/files/he/web/javascript/reference/global_objects/array/from/index.html

---
title: ()Array.from
slug: Web/JavaScript/Reference/Global_Objects/Array/from
translation_of: Web/JavaScript/Reference/Global_Objects/Array/from
---
<div>מתודת ה-</div>

<div dir="ltr"><code><strong>Array.from()</strong></code><strong> </strong></div>

<div>יוצרת מערך חדש שהוא העתק בעומק אחד (לא יכלול את האובייקטים אליהם יש הפניות מאיברים במערך הנתון) של המערך או אובייקט איטרבילי המועבר כפרמטר.</div>

<div dir="rtl"></div>

<div>{{EmbedInteractiveExample("pages/js/array-from.html")}}</div>



<h2 id="Syntax">Syntax</h2>

<pre class="brush: js">Array.from(arrayLike[, mapFn[, thisArg]])
</pre>

<h3 id="Parameters">Parameters</h3>

<dl>
 <dt><code>arrayLike</code></dt>
 <dd>An array-like or iterable object to convert to an array.</dd>
 <dt><code>mapFn</code> {{Optional_inline}}</dt>
 <dd>Map function to call on every element of the array.</dd>
 <dt><code>thisArg</code> {{Optional_inline}}</dt>
 <dd>Value to use as <code>this</code> when executing <code>mapFn</code>.</dd>
</dl>

<h3 id="Return_value">Return value</h3>

<p>A new {{jsxref("Array")}} instance.</p>

<h2 id="Description">Description</h2>

<p><code>Array.from()</code> lets you create <code>Array</code>s from:</p>

<ul>
 <li>array-like objects (objects with a <code>length</code> property and indexed elements) or</li>
 <li><a href="/en-US/docs/Web/JavaScript/Guide/iterable">iterable objects</a> (objects where you can get its elements, such as {{jsxref("Map")}} and {{jsxref("Set")}}).</li>
</ul>

<p><code>Array.from()</code> has an optional parameter <code>mapFn</code>, which allows you to execute a {{jsxref("Array.prototype.map", "map")}} function on each element of the array (or subclass object) that is being created. More clearly,<code> Array.from(obj, mapFn, thisArg)</code> has the same result as <code>Array.from(obj).map(mapFn, thisArg)</code>, except that it does not create an intermediate array. This is especially important for certain array subclasses, like <a href="/en-US/docs/Web/JavaScript/Typed_arrays">typed arrays</a>, since the intermediate array would necessarily have values truncated to fit into the appropriate type.</p>

<p>The <code>length</code> property of the <code>from()</code> method is 1.</p>

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

<h2 id="Examples">Examples</h2>

<h3 id="Array_from_a_String">Array from a <code>String</code></h3>

<pre class="brush: js">Array.from('foo');
// [ "f", "o", "o" ]</pre>

<h3 id="Array_from_a_Set">Array from a <code>Set</code></h3>

<pre class="brush: js">const set = new Set(['foo', 'bar', 'baz', 'foo']);
Array.from(set);
// [ "foo", "bar", "baz" ]</pre>

<h3 id="Array_from_a_Map">Array from a <code>Map</code></h3>

<pre class="brush: js">const map = new Map([[1, 2], [2, 4], [4, 8]]);
Array.from(map);
// [[1, 2], [2, 4], [4, 8]]

const mapper = new Map([['1', 'a'], ['2', 'b']]);
Array.from(mapper.values());
// ['a', 'b'];

Array.from(mapper.keys());
// ['1', '2'];
</pre>

<h3 id="Array_from_an_Array-like_object_(arguments)">Array from an Array-like object (arguments)</h3>

<pre class="brush: js">function f() {
  return Array.from(arguments);
}

f(1, 2, 3);

// [ 1, 2, 3 ]</pre>

<h3 id="Using_arrow_functions_and_Array.from">Using arrow functions and <code>Array.from</code></h3>

<pre class="brush: js">// Using an arrow function as the map function to
// manipulate the elements
Array.from([1, 2, 3], x =&gt; 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) =&gt; i);
// [0, 1, 2, 3, 4]
</pre>

<h3 id="Sequence_generator_(range)">Sequence generator (range)</h3>

<pre class="brush: js">// Sequence generator function (commonly referred to as "range", e.g. Clojure, PHP etc)
const range = (start, stop, step) =&gt; Array.from({ length: (stop - start) / step + 1}, (_, i) =&gt; start + (i * step));

// Generate numbers range 0..4
range(0, 4, 1);
// [0, 1, 2, 3, 4]

// Generate numbers range 1..10 with step of 2
range(1, 10, 2);
// [1, 3, 5, 7, 9]

// Generate the alphabet using Array.from making use of it being ordered as a sequence
range('A'.charCodeAt(0), 'Z'.charCodeAt(0), 1).map(x =&gt; String.fromCharCode(x));
// ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
</pre>

<h2 id="Polyfill">Polyfill</h2>

<p><code>Array.from</code> 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 <code>Array.from</code> in implementations that don't natively support it. This algorithm is exactly the one specified in ECMA-262, 6th edition, assuming <code>Object</code> and <code>TypeError</code> have their original values and that <code>callback.call</code> evaluates to the original value of {{jsxref("Function.prototype.call")}}. 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.</p>

<pre class="brush: js">// Production steps of ECMA-262, Edition 6, 22.1.2.1
if (!Array.from) {
  Array.from = (function () {
    var toStr = Object.prototype.toString;
    var isCallable = function (fn) {
      return typeof fn === 'function' || toStr.call(fn) === '[object Function]';
    };
    var toInteger = function (value) {
      var number = Number(value);
      if (isNaN(number)) { return 0; }
      if (number === 0 || !isFinite(number)) { return number; }
      return (number &gt; 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 &gt; 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 &gt; 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 &lt; len… (also steps a - h)
      var kValue;
      while (k &lt; len) {
        kValue = items[k];
        if (mapFn) {
          A[k] = typeof T === 'undefined' ? mapFn(kValue, k) : mapFn.call(T, 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;
    };
  }());
}
</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-array.from', 'Array.from')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
  <tr>
   <td>{{SpecName('ES2015', '#sec-array.from', 'Array.from')}}</td>
   <td>{{Spec2('ES2015')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>



<p>{{Compat("javascript.builtins.Array.from")}}</p>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Array")}}</li>
 <li>{{jsxref("Array.prototype.map()")}}</li>
 <li>{{jsxref("TypedArray.from()")}}</li>
</ul>