Getting key with the highest value from object

Question

I have a object like that one:

Object {a: 1, b: 2, undefined: 1}  

How can I quickly pull the largest value identifier (here: b) from it? I tried converting it to array and then sorting, but it didn't work out, since it got sorted alphabetically (and it seems like a overkill to juggle data back and forth just for getting one value out of three).

Answer 1

For example:

var obj = {a: 1, b: 2, undefined: 1};  Object.keys(obj).reduce(function(a, b){ return obj[a] > obj[b] ? a : b }); 

In ES6:

var obj = {a: 1, b: 2, undefined: 1};  Object.keys(obj).reduce((a, b) => obj[a] > obj[b] ? a : b); 

Answer 2

Using Underscore or Lo-Dash:

var maxKey = _.max(Object.keys(obj), function (o) { return obj[o]; }); 

With ES6 Arrow Functions:

var maxKey = _.max(Object.keys(obj), o => obj[o]); 

jsFiddle demo