The Array.isArray()
method determines whether the passed value is an Array
.
Array.isArray([1, 2, 3]); // true Array.isArray({foo: 123}); // false Array.isArray('foobar'); // false Array.isArray(undefined); // false
Syntax
Array.isArray(value)
Parameters
value
- The value to be checked.
Return value
true
if the value is an Array
; otherwise, false
.
Description
If the value is an Array
, true
is returned; otherwise, false
is.
See the article โDetermining with absolute accuracy whether or not a JavaScript object is an arrayโ for more details. Given a TypedArray
instance, false
is always returned.
Polyfill
Running the following code before any other code will create Array.isArray()
if it's not natively available.
if (!Array.isArray) { Array.isArray = function(arg) { return Object.prototype.toString.call(arg) === '[object Array]'; }; }
Examples
Using Array.isArray
// all following calls return true Array.isArray([]); Array.isArray([1]); Array.isArray(new Array()); Array.isArray(new Array('a', 'b', 'c', 'd')); Array.isArray(new Array(3)); // Little known fact: Array.prototype itself is an array: Array.isArray(Array.prototype); // all following calls return false Array.isArray(); Array.isArray({}); Array.isArray(null); Array.isArray(undefined); Array.isArray(17); Array.isArray('Array'); Array.isArray(true); Array.isArray(false); Array.isArray(new Uint8Array(32)); Array.isArray({ __proto__: Array.prototype });
instanceof
vs isArray
When checking for Array
instance, Array.isArray
is preferred over instanceof
because it works through iframes
.
var iframe = document.createElement('iframe'); document.body.appendChild(iframe); xArray = window.frames[window.frames.length-1].Array; var arr = new xArray(1,2,3); // [1,2,3] // Correctly checking for Array Array.isArray(arr); // true // Considered harmful, because doesn't work through iframes arr instanceof Array; // false
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Array.isArray' in that specification. |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
isArray | Chrome Full support 5 | Edge Full support 12 | Firefox Full support 4 | IE Full support 9 | Opera Full support 10.5 | Safari Full support 5 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 14 | Safari iOS Full support 5 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.1.100 |
Legend
- Full support
- Full support