实现js版StringBuilder

.net中StringBuilder的好处不多说了，下面是js版的StringBuilder

function StringBuilder() {
            this.__stringArr__ = [];
        }
        $.extend(StringBuilder.prototype, {
            append: function (str) {
                this.__stringArr__.push(str);
            },
            appendFormat: function (str) {
                for (var i = 1,len=arguments.length; i < len; i++) {
                    var reg = new RegExp("\{"+(i-1)+"\}","g");
                    str = str.replace(reg,arguments[i]);
                }
                this.__stringArr__.push(str);
            },
            toString: function () {
                return this.__stringArr__.join("");
            },
            clear: function () {
                this.__stringArr__ = [];
            }
        });

调用：

 var sb = new StringBuilder();
 
         sb.append("1-");
 
         sb.appendFormat("2:{0}", "hello");
 
         console.info(sb.toString());