Empty JS Object

Question

Is there a better way to check if an object is empty? I'm using this:

function isObjEmpty(obj)
{
    for (var p in obj) return false;
    return true;
}

Why to use [hasOwnProperty](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/HasOwnProperty) => ref: http://jsfiddle.net/v3Lyn/ — Yoshi, May 07 '12 at 13:38
possible duplicate of [How do I test for an empty Javascript object from JSON?](http://stackoverflow.com/questions/679915/how-do-i-test-for-an-empty-javascript-object-from-json) — Felix Kling, May 07 '12 at 13:52

score 10 · Accepted Answer · answered May 07 '12 at 13:36

10

If you're looking for a one-liner, consider Object.keys:

var isEmpty = !Object.keys(obj).length;

Your current method is dangerous, since it will always return false when Object.prototype has been extended: http://jsfiddle.net/Neppc/

answered May 07 '12 at 13:36

Rob W

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yes. you are right. wating 10min to mark your answer as correct. cant yet. thanks rob. – Rodrigo Manguinho May 07 '12 at 13:44
This is 10 times slower tha the (for...in) option :) See http://stackoverflow.com/questions/4994201/is-object-empty?lq=1 – davidhadas Dec 28 '15 at 10:44

score 2 · Answer 2 · answered May 07 '12 at 14:00

2

Another option is built into jQuery: jQuery.isEmptyObject(obj)

Edit: Interestingly, that implementation is the same as your code in the question.

answered May 07 '12 at 14:00

Anna Brenden

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score 0 · Answer 3 · edited May 23 '17 at 12:18

Actually this is a very good way to check if an object is empty! And it is 10 times faster for exmpty objects than using Object.keys() as suggested above :)

Tested under Node, Chrom, Firefox and IE 9, it becomes evident that for most use cases:

(for...in...) is the fastest option to use!
Object.keys(obj).length is 10 times slower for empty objects
JSON.stringify(obj).length is always the slowest (not suprising)
Object.getOwnPropertyNames(obj).length takes longer than Object.keys(obj).length can be much longer on some systems.

Bottom line performance wise, use:

function isEmpty(obj) { 
   for (var x in obj) { return false; }
   return true;
}

or

function isEmpty(obj) {
   for (var x in obj) { if (obj.hasOwnProperty(x))  return false; }
   return true;
}

See detailed testing results and test code at Is object empty?

Empty JS Object

3 Answers3