function StringBuffer() {   this._strs = new Array; } StringBuffer.prototype.append = function (str) {   this._strs.push(str); }; StringBuffer.prototype.toString = function() {   return this._strs.join(""); };

var sb=new StringBuffer();sb.append("sss")sb.append("ddd");sb.toString(); //"sssddd"

/***  格式化字符串*  format("{0},{1}","ddd","fff");*  format('<button id="{0}" type="{1}">{2}</button>',"btnOk","Button","Ok")**/function format(str){  for(var i=0;i<arguments.length-1;i++){    var placeHolder="{"+i+"}";    if(str.indexOf(placeHolder)!=-1){      str=str.replace(placeHolder,arguments[i+1]);    }  }  return str;}