Length of a JavaScript object

Question

I have a JavaScript object. Is there a built-in or accepted best practice way to get the length of this object?

const myObject = new Object();
myObject["         


        

Answer 1

You can always do Object.getOwnPropertyNames(myObject).length to get the same result as [].length would give for normal array.

Answer 2

The simplest way is like this:

Object.keys(myobject).length

Where myobject is the object of what you want the length of.

Answer 3

Below is a version of James Coglan's answer in CoffeeScript for those who have abandoned straight JavaScript :)

Object.size = (obj) ->
  size = 0
  size++ for own key of obj
  size

Answer 4

If we have the hash

hash = {"a" : "b", "c": "d"};

we can get the length using the length of the keys which is the length of the hash:

keys(hash).length

Answer 5

A nice way to achieve this (Internet Explorer 9+ only) is to define a magic getter on the length property:

Object.defineProperty(Object.prototype, "length", {
    get: function () {
        return Object.keys(this).length;
    }
});

And you can just use it like so:

var myObj = { 'key': 'value' };
myObj.length;

It would give 1.

Answer 6

This method gets all your object's property names in an array, so you can get the length of that array which is equal to your object's keys' length.

Object.getOwnPropertyNames({"hi":"Hi","msg":"Message"}).length; // => 2