Array.isArray()

Summary

The Array.isArray() method 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

See the article "Determining with absolute accuracy whether or not a JavaScript object is an array" for more details.

Examples

// all following calls return true
Array.isArray([]);
Array.isArray([1]);
Array.isArray( new Array() );
// 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({ __proto__ : Array.prototype });

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]';
  };
}

Specifications

Browser compatibility

Based on Kangax's compat table.

See also

• Array