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

function get(){ 
var a = "23.456322"; 
var aNew; 
var re = /([0-9]+\.[0-9]{2})[0-9]*/; 
aNew = a.replace(re,"$1"); 
alert(aNew); 
}

function get(){ 
var num=22.127456; 
alert( Math.round(num*100)/100); 
}

function get(){ 
var num = new Number(13.37); 
num = num.toFixed(2);//2为要获取小数后的位数 会自动四舍五入 
alert(num); 
}