Sort a Javascript Array by frequency and then filter repeats

Question

What is an elegant way to take a javascript array, order by the frequency of the values, and then filter for uniques?

So,

[\"apples\", \"oranges\", \"o

Answer 1

for the first step to compute

{
    oranges: 4,
    bananas: 2,
    apples: 1
}

you can use countBy function of underscroe.js

var all=["apples", "oranges", "oranges", "oranges", "bananas", "bananas", "oranges"];
var frequency=_.countBy(all,function(each){return each});

so frequency object will contain frequency of all unique values, and you can get an unique list by simply calling _.uniq(all), and to sort that unique list by the _.sortBy method of underscore and using your frequency object you can use

_.sortBy(_.uniq(all),function(frequencyKey){return -frequency[frequencyKey]});

-ve sign is used here to sort the list in decending order by means of frequency value as per your requirement.

You can check the the documentation of http://underscorejs.org/ for further optimization by your own trick :)