JSFiddle - React, Tailwind, and code Playground

JavaScript

(function (old) {
        Number.prototype.toLocaleString = function () {
            var n = old.apply(1000);
            if (n.length == 8) // IE's implementation, good enough for us
                return old.apply(this);
            else if (n.length == 5) { // Fx's implementation, needs a little work
                return old.apply(this).slice(0,-3) + this.toFixed(2).slice(-3);
            } else { // Other implementations
                var f = this.toFixed(2).slice(-3); 
                var s = f.substring(0,1) == "." ? "," : ".";
                return this.toFixed(2).slice(0,-3).replace(/(?=(?:\d{3})+(?!\d))/g, s) + f;
            }
        }
    })(Number.prototype.toLocaleString);
        
alert(10000000.12.toLocaleString());