Easiest way to format number to using JavaScript

 var currency = $(sender).val();
            var _amtToVal = (Math.round(currency * 100) / 100).toFixed(2);//.toLocaleString('en-US');
            var _ForamtValue = _amtToVal.toString().replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,");

Where sender is the control id

var currency = $('#sender').val();