用js实现StringBuffer连接字符串

function StringBuffer(){//自定义一个StringBuffer类。以便提高String的连接字符串性能
this._strings = new Array;
}
StringBuffer.prototype.append = function(str){
this._strings.push(str);
}
StringBuffer.prototype.toString = function(){
return this._strings.join("");//join()用参数里面的字符串连接Array里面的值
}

function test(){
var strb = new StringBuffer();
strb.append("hello");
strb.append("world");
alert(strb.toString());
}