JSFiddle - React, Tailwind, and code Playground

JavaScript

(function (old) {
    var dec = 0.12 .toLocaleString().charAt(1),
        tho = dec === "." ? "," : ".";
    
    if (1000 .toLocaleString() !== "1,000.00") {
        Number.prototype.toLocaleString = function () {
           var f = this.toFixed(2).slice(-2); 
           return this.toFixed(2).slice(0,-3).replace(/(?=(?!^)(?:\d{3})+(?!\d))/g, tho) + dec + f;
        }
    }
})(Number.prototype.toLocaleString);

document.body.innerHTML = 10000 .toLocaleString() + "<br/>" + 123456.789 .toLocaleString();