JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="formattedNumberField" value="" />

JavaScript

var fnf = document.getElementById("formattedNumberField");
fnf.addEventListener('keyup', function(evt){
    var n = parseInt(this.value.replace(/\D/g,''),10);
    fnf.value = n.toLocaleString();
}, false);