Identifying Array Object

Question

How to know whether an object is array or not?

 var x=[];

console.log(typeof x);//output:"object"
alert(x);//output:[object Object]
console.log(x.valueOf())//output:<blank>? what is the reason here?
console.log([].toString()); also outputs <blank>     
Object.prototype.toString.call(x) output:[object Array] how?

since console.log([].toString()); outputs :blank

1st:

why i get blank at 2nd last statement?

2nd:

Is there a way to know exactly what an object is: Array or plain Object({}) without the help of their respective methods like x.join() indicates x is an Array,not in this way.

Actually,in jquery selection like $("p") returns jquery object so if i use

console.log(typeof $("p"));//output:"object

I just wanted to know the actual Name of the Object.Thats it.Thank u for u help

Take a look into this other question http://stackoverflow.com/questions/767486/how-do-you-check-if-a-variable-is-an-array-in-javascript — acj, Apr 26 '13 at 11:18

score 13 · Accepted Answer · answered Apr 26 '13 at 11:18

13

In pure JavaScript you can use the following cross browser approach:

if (Object.prototype.toString.call(x) === "[object Array]") {
    // is plain array
}

jQuery has special method for that:

if ($.isArray(x)) {
    // is plain array
}

answered Apr 26 '13 at 11:18

VisioN

143,310
32
282
281

console.log([].valueOf())//output:? what is the reason here? – Maizere Pathak.Nepal Apr 26 '13 at 11:25
@Maizere Basically `[].valueOf()` returns `[]`, and doesn't make any sense here. – VisioN Apr 26 '13 at 11:27
@Maizere Glad it helped. FYI, jQuery has also [`$.isPlainObject()`](http://api.jquery.com/jQuery.isPlainObject/) for objects check. – VisioN Apr 26 '13 at 11:37
Object.prototype.toString.call(x) output:[object Array] how? since console.log([].toString()); outputs :blank – Maizere Pathak.Nepal Apr 26 '13 at 11:39
@Maizere Because `Object.prototype.toString` is not the same as `Array.prototype.toString`. The latter simply stringifies array, e.g. `[1,2,3].toString() === "1,2,3"`. – VisioN Apr 26 '13 at 11:41
what will a former do than? – Maizere Pathak.Nepal Apr 26 '13 at 11:45
@Maizere It gets a string that represents array as a JavaScript object. You can read more at [**MDN**](https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/toString#Using_toString_to_detect_object_type). – VisioN Apr 26 '13 at 11:56

score 4 · Answer 2 · edited Aug 17 '16 at 08:12

4

You can use instanceof. Here's some FireBug testing:

test1 = new Object();
test2 = new Array();
test3 = 123;

console.log(test1 instanceof Array); //false
console.log(test2 instanceof Array); //true
console.log(test3 instanceof Array); //false

edited Aug 17 '16 at 08:12

Al Foиce ѫ

4,195
12
39
49

answered Apr 26 '13 at 11:22

LeonardChallis

7,759
6
45
76

1

Maybe the downvoter would be kind enough to explain why the -1, for the sake of learning :) – LeonardChallis Apr 26 '13 at 11:25
1

Wasn't me (frankly I don't think this is wrong enough to deserve a downvote), but this fails in multi-DOM environments such as iframes and the like. See [this article](http://perfectionkills.com/instanceof-considered-harmful-or-how-to-write-a-robust-isarray/) for more. – Asad Saeeduddin Apr 26 '13 at 11:30
It is a simple and clean solution which works in my scenario. Tested on latest version of Chrome and Firefox. Thanks – Aryan Firouzian Jan 14 '19 at 10:19

score 2 · Answer 3 · answered Apr 26 '13 at 11:19

Best practice is the invocation of Object.prototype.toString() on the target object, which displays the internal [[Class]] property name.

Object.prototype.toString.call( x ); // [object Array]

This has the adventage, that it works on any and every object, regardless of if you're working in a multi frame / window environment, which causes problems on using x instanceof Array.

Newer ES5 implementations, also give you the method Arrays.isArray(), which returns true or false.

Array.isArray( x ); // true

And last but not least, jQuery has its very own .isArray() method, which also returns a boolean

jQuery.isArray( x ); // true

score 1 · Answer 4 · answered Apr 26 '13 at 11:18

1

Simple:

if( Object.prototype.toString.call( someVar ) === '[object Array]' ) {
    alert( 'Array!' );
}

answered Apr 26 '13 at 11:18

basarat

261,912
58
460
511

score 1 · Answer 5 · answered Apr 26 '13 at 11:21

1

http://api.jquery.com/jQuery.isArray/

if($.isArray(x)){
  alert("isArray");
}

answered Apr 26 '13 at 11:21

Adil Shaikh

44,509
17
89
111

score 0 · Answer 6 · answered Apr 26 '13 at 11:20

0

I think you are searching for something like this:

if( Object.prototype.toString.call( someVar ) === '[object Array]' ) {
    alert( 'Array!' );
}

Hope this helps. A little to slow :P

answered Apr 26 '13 at 11:20

s_qw23

354
2
11

1

Yes, this has already been posted two or three times. – Asad Saeeduddin Apr 26 '13 at 11:21

Identifying Array Object

6 Answers6