Formatting CartoCSS function

gistfile1.txt

String.prototype.format = (function (i, safe, arg) {
            function format() {
                var str = this,
                    len = arguments.length + 1;

                for (i = 0; i < len; arg = arguments[i++]) {
                    safe = typeof arg === 'object' ? JSON.stringify(arg) : arg;
                    str = str.replace(RegExp('\\{' + (i - 1) + '\\}', 'g'), safe);
                }
                return str;
            }

            //format.native = String.prototype.format;
            return format;
            
        })();