JSFiddle - React, Tailwind, and code Playground

HTML

<div id="res"></div>

JavaScript

var ar = {};
ar['a']=4;
ar['b']=5;
ar['c']=2;
ar['d']=2;
ar['e']=1;

var result = [];
for (var letter in ar)
    result.push([letter, ar[letter]]);

result.sort(function(x,y){return y[1]-x[1]});

var str = '';

for (var idx in result)
    str += result[idx][0];

document.getElementById('res').innerHTML = str;