1. substring

function get()
{
var s = 22.127456 + "";
var str = s.substring(0,s.indexOf(".") + 3);
alert(str);
}

　　2. 正则表达式

<script type="text/javascript">
onload = function(){
var a = "23.456322";
var aNew;
var re = /([0-9]+\.[0-9]{2})[0-9]*/;
aNew = a.replace(re,"$1");
alert(aNew);
}
</script>

　　3. Math.round

<script>
var num=22.127456;
alert(Math.round(num*100)/100);
</script>

　　4.num.toFixed（需要IE5.5+才支持）

<script>
var num=22.127456;
alert(num.toFixed(2));
</script>