Object iteration in reverse (javascript)

Question

How can I iterate over a javascript object, from back to front.

The object looks like this. {"33":140, "34":100, "35":120, "36":200}

I want it to display like this...

I tried sorting first then displaying, but it sorts by the second number, not the key. How would I either iterate from back to front, or reverse sort based on the key.

I realize this is pretty simple, but Im getting pretty frustrated with it....

There is no guarantee on the order when you iterate object properties. And you cannot sort objects. I believe you'll have to use an array of objects, and sort that. — bfavaretto
– bfavaretto, Commented Aug 23, 2013 at 21:36
@bfavaretto Correct, objects are not ordered -- but we sure can use the keys, sort them and use that (see my answer). — Ingo Bürk
– Ingo Bürk, Commented Aug 23, 2013 at 21:40
@IngoBürk I did, and upvoted your answer. That's indeed the best approach. — bfavaretto
– bfavaretto, Commented Aug 23, 2013 at 21:42
@bfavaretto Yeah, I didn't notice at first that both comments were you. D'oh. :) — Ingo Bürk
– Ingo Bürk, Commented Aug 23, 2013 at 21:43
One thing I learned today, objects are ordered, just not in the order they are defined. — Andy
– Andy, Commented Aug 23, 2013 at 22:07

Ingo Bürk · Accepted Answer · 2013-08-23 21:48:41Z

5

A fairly modern version would look like this:

Object.keys(obj).sort(function (a, b) {
    return Number(b) - Number(a);
}).forEach(function (current) { 
    console.log(current + ' | ' + obj[current]); 
});

Similarly, but with a little bit more code, it could be written for older browsers, too. Or you use shims.

edited Aug 23, 2013 at 21:48

answered Aug 23, 2013 at 21:37

Ingo Bürk

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5 Comments

bfavaretto Over a year ago

This is really close to what the OP actually need (console.log(obj[current]))

Ingo Bürk Over a year ago

He wanted to log both. I just thought I wouldn't take all the fun out of it. It solves the actual problem, he can deal with the output.

Kylie Over a year ago

Thanks!!...very efficient, and compact.....much better than the solution I was busy cooking up...which relied on alternate arrays, and two loops, in a cumbersome function

Ingo Bürk Over a year ago

@bfavaretto Since you already wrote the other part, I updated my answer. :)

user2437417 Over a year ago

The sort may fail if some of the numbers have 1 or 3 digits instead of 2. If that's the case, OP will need to pass a function and do an actual numeric comparison. Then the .reverse() could be eliminated as well.

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