JavaScript way to tell if an object is an Array [duplicate]

Question

What's the 'right' way to tell if an object is an Array?

function isArray(o) { ??? }

Answer 1

The best way:

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

The ECMAScript 5th Edition Specification defines a method for that, and some browsers, like Firefox 3.7alpha, Chrome 5 Beta, and latest WebKit Nightly builds already provide a native implementation, so you might want to implement it if not available:

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

Answer 2

You should be able to use the instanceof operator:

var testArray = [];

if (testArray instanceof Array)
    ...

Answer 3

jQuery solves lots of these sorts of issues:

jQuery.isArray(obj)

Answer 4

This is what I use:

function is_array(obj) {
  return (obj.constructor.toString().indexOf("Array") != -1)
}

Answer 5

function typeOf(obj) {
  if ( typeof(obj) == 'object' )
    if (obj.length)
      return 'array';
    else
      return 'object';
    } else
  return typeof(obj);
}

Answer 6

You can take take Prototype library definition of method Object.isArray() which test it :

function(object) {
  return object != null && typeof object == "object" &&
   'splice' in object && 'join' in object;
}