Introduced in JavaScript 1.8.5

Summary

Returns true if an object is an array, false if it is not.

Syntax

Array.isArray(obj)

Parameters

obj

The object to be checked

Description

This function is part of the ECMAScript 5 standard. See the Web Tech Blog for more details.

Examples

// all following calls return true
Array.isArray([]);
Array.isArray([1]);
Array.isArray( new Array() );
Array.isArray( Array.prototype ); // Little known fact: Array.prototype itself is an array.

// 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);

Compatibility

Running the following code before any other code will create Array.isArray if it's not natively available. This relies on Object.prototype.toString being unchanged and call resolving to the native Function.prototype.call method.

if(!Array.isArray) {
  Array.isArray = function (arg) {
    return Object.prototype.toString.call(arg) == '[object Array]';
  };
}

Cross-browser compatibility

Based on Kangax's compat table.

See also

• Bug 510537 - ES5: Array.isArray