JSFiddle - React, Tailwind, and code Playground

HTML

<div id="display"></div>

JavaScript

var text = '';
var chars = 'abcdefghijklmnopqrstuvwxyz';
var cnt = new Array(chars.length);
for (var i = 0; i < cnt.length; i++) cnt[i] = 0;

var handle = window.setInterval(function(){
    var ch = Math.floor(Math.random() * chars.length);
    cnt[ch]++;
    text += chars.charAt(ch);
    $('#display').text(text);
    if (text.length == 20) window.clearInterval(handle);
}, 2000);