Difference between array and object in javascript? or Array Vs Object

Question

How to recognize array & object in js where typeof doesn’t come in handy?

 var arr = [], ob = {};

As everything in js are objects,

Answer 1

There are multiple ways of differentiating between array and object, some on them are already mentioned above i would like to just add on above answers.

First Approach Differentiation using length, length property exist on Array but doesn't exist on Object

 var arr = [1,2,3];  arr.length => 3

 var obj = {name: 'name'}; obj.length => undefined

Note: This approach fails when someone declares object like below, we can use this approach only when we are sure we will not get any object having length property

var rectangle = {length: 50, width: 50}; rectangle.length => 50

Second Approach Using instanceof Array

var arr = [1,2,3]; arr instanceof Array => true
var obj = {name: 'name'}; ojb instanceof Array => false 

Third Approach Using Array.isArray, this is most preferable approach and is supported by most of browser now

Note: Array.isArray is preferred over instanceof because it works through iframes.

Array.isArray(arr) => true
true
Array.isArray(obj) => false

If you want to support i.e 8 browser the use Object.prototype.toString We can write polyfill for i.e 8

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

Object.prototype.toString.call(arr); =>"[object Array]"
Object.prototype.toString.call(obj); =>"[object Object]"

Reference: isArray