List all variable names in a object

Question

I have this object:

var sub = {
    0:  [""],
    21: ["Look, here, are three little stuff,","ready to sing for this crowd"],
    28: ["Listen up, 'cause here's our story","I'm gonna sing it very LOUUU..."],
    36: [""],
    45: ["VERY LOUUU..."],
    48: [""],
    61: ["When you're a younger stuff","and your stuff is very bare"],
    68: ["Feels like the sun will never come","when your stuff's not there"],
    74: ["So the three of us will fight the fight","there is nothing that we fear"],
    80: ["We'll have to figure out what we'll do next","till our stuff is here!"],
    87: ["We are the guys","on a quest to find out who we are"],
    94: ["And we will never stop the journey","not until we have our stuff"],
    101:[""],
    106:["(stuff...)"],
}
//I like stuff.

And I would like to get all of the variable names into an array, like so:

variables == [0, 21, 28, 36, 45, 48, 61, 68, 74, 80, 87, 94, 101, 106, 109];

Is there a built in function for this, or is it possible to iterate over JSON object variables?

This is a JavaScript object, not a JSON object! Please read [There's no such thing as a "JSON Object"](http://benalman.com/news/2010/03/theres-no-such-thing-as-a-json/). — Felix Kling, Feb 22 '13 at 19:32
Objects have *properties*, not variables. What you are looking for is the *names* of the properties. — , Feb 22 '13 at 19:35
Following the solution in the linked question will give you an array of strings though. If you want to convert them to numbers, have a look at http://stackoverflow.com/questions/2130454/javascript-to-convert-string-to-number. — Felix Kling, Feb 22 '13 at 19:36

score 6 · Accepted Answer · answered Feb 22 '13 at 20:01

6

Most browsers have this method built right into the Object prototype.

You can use

var variables = Object.keys(sub); //returns an array with all the object keys

Hope that helps!

answered Feb 22 '13 at 20:01

KDV

730
1
6
12

Awesome! I like this solution better since it doesn't require `for` loops. – SeinopSys Feb 22 '13 at 20:05
This will return an array of string though – Mohsen Feb 22 '13 at 22:36
Thanks this helped me! really good awsner instead of using loops – Bas Mienis Sep 30 '21 at 07:39

Mohsen · Answer 2 · 2013-02-22T20:10:48.783

1

var variables = [];
for (var i in sub) {
 if (sub.hasOwnProperty(i)){
  variables.push(+i);
 }
}

This is a manual solution. I recommend you using Underscore.js for problems like this. There is a good _.keys method in Underscore.

edited Feb 22 '13 at 20:10

answered Feb 22 '13 at 19:31

Mohsen

64,437
34
159
186

1

I'd drop a `.hasOwnProperty` here too. – Kos Feb 22 '13 at 19:35
Just be aware this will 1) return `["94", "21", "36", ..]` due to the `[ToString]` of *property* names; and 2) the order is *not* guaranteed. – Feb 22 '13 at 19:36
@pst Is there a way to create the new array in a way that the order is precise? – SeinopSys Feb 22 '13 at 19:41
@DJDavid98: No, object properties have no specific order. It's like a hash map. – Felix Kling Feb 22 '13 at 19:47
1

@FelixKling I guess I can use a `.sort()` on it, so it will be all good. – SeinopSys Feb 22 '13 at 19:48
@DJDavid98: Of course, if the property names are sortable, like in your example, then yes. – Felix Kling Feb 22 '13 at 19:49
@Kos and @ pst you are both right. Updated! – Mohsen Feb 22 '13 at 20:11

List all variable names in a object

2 Answers2