function format(input) { // input.value = (input.value).toLocaleString('en-US'); var nStr = input.value + ""; nStr = nStr.replace(/\,/g, ""); x = nStr.split("."); x1 = x[0]; x2 = x.length > 1 ? "." + x[1] : ""; var rgx = /(\d+)(\d{3})/; while (rgx.test(x1)) { x1 = x1.replace(rgx, "$1" + "," + "$2"); } input.value = x1 + x2; }