Javascript StringBuffer类的实现是通过prototype构造一个StringBuffer类，代码如下：
function StringBuffer() {
this.__strings__ = new Array();
}
StringBuffer.prototype.append = function(str) {
this.__strings__.push(str);
};
StringBuffer.prototype.toString = function() {
return this.__strings__.join("");
};
例子：
<html>
<head>
<title>test</title>
<script type="text/javascript">
function StringBuffer() {
this.__strings__ = new Array();
}
StringBuffer.prototype.append = function(str) {
this.__strings__.push(str);
};
StringBuffer.prototype.toString = function() {
return this.__strings__.join("");
};
function testStringBuffer(){
var date1 = new Date();
var str;
for( var i=0; i<10000; i++){
str += "text";
}
var date2 = new Date();
document.writeln("Sting use time:"+ (date2 - date1) +"ms");
//StringBuffer
var date3 = new Date();
var strBuffer = new StringBuffer();
for(i=0; i<10000; i++){
strBuffer.append("text");
}
strBuffer.toString();
var date4 = new Date();
document.writeln("<br/>StringBuffer use time:"+ (date4 - date3) +"ms");
}
</script>
</head>
<body>
<input type="button" value="testStringBuffer" onclick="testStringBuffer()"/>
</body>
</html>