JavaScript Way To Tell If An Object Is An Array

What's the 'right' way to tell if an object is an Array? function isArray(o) { ??? }

Solution 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]';
  };
}

Solution 2:

You should be able to use the instanceof operator:

var testArray = [];

if (testArray instanceof Array)
    ...

Solution 3:

jQuery solves lots of these sorts of issues:

jQuery.isArray(obj)

Solution 4:

This is what I use:

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

Solution 5:

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