what are the conditions to be a true array

Question

Javascript do not have true array. because when i tested out this thing in google console i was surprised to see that there is no difference between an object and an array.

var obj = {};
var arr = [];

typeof obj; //object
typeof arr; //object

i am curious to know

why this is so?

and

Do really javascript possess false array?

and

Is this typeof is wrong , i mean do this not differentiate between object and an array?

and

what are the conditions to be a true array?

thanks!

Answer 1

JavaScript is a dynamic language and its objects are very flexible. And there is really no gurantee that, an object you have is of particular type. Because we can do duck typing .

If you want to know if an object is an Array or not, you can use this

Object.prototype.toString.call(obj) == '[object Array]';

This is taken from the underscore.js library's _.isArray function. Since it is popular and widely used, this method should be reliable.

If your environment supports ECMA 5.1, then you can also use Array.isArray function, like this

Array.isArray(obj);