formatNumber = function (number) {
        number = String(number).replace(new RegExp(/\s/g), '');
        var length = number.length;
        var x = number.split('.');
        var x1 = x[0];
        var x2 = x.length > 1 ? '.' + x[1] : '';
        var rgx = /(\d+)(\d{3})/;
        while (rgx.test(x1)) {
            x1 = x1.replace(rgx, '$1' + '.' + '$2');
        }
        return x1 + x2;
    }

Thanks to http://www.mredkj.com/javascript/numberFormat.html#addcommas

format thousands

number, format

JavaScript