javascript 保留2位小数

    <script type="text/javascript">   
            //保留两位小数    
            //功能：将浮点数四舍五入，取小数点后2位   
            function toDecimal(x) {   
                var f = parseFloat(x);   
                if (isNaN(f)) {   
                    return;   
                }   
                f = Math.round(x*100)/100;   
                return f;   
            }   
       
       
            //制保留2位小数，如：2，会在2后面补上00.即2.00   
            function toDecimal2(x) {   
                var f = parseFloat(x);   
                if (isNaN(f)) {   
                    return false;   
                }   
                var f = Math.round(x*100)/100;   
                var s = f.toString();   
                var rs = s.indexOf('.');   
                if (rs < 0) {   
                    rs = s.length;   
                    s += '.';   
                }   
                while (s.length <= rs + 2) {   
                    s += '0';   
                }   
                return s;   
            }   
               
            function fomatFloat(src,pos){      
                 return Math.round(src*Math.pow(10, pos))/Math.pow(10, pos);      
            }   
            //四舍五入   
            alert("保留2位小数：" + toDecimal(3.14159267));   
            alert("强制保留2位小数：" + toDecimal2(3.14159267));   
            alert("保留2位小数：" + toDecimal(3.14559267));   
            alert("强制保留2位小数：" + toDecimal2(3.15159267));   
            alert("保留2位小数：" + fomatFloat(3.14559267, 2));   
            alert("保留1位小数：" + fomatFloat(3.15159267, 1));   
               
            //五舍六入   
            alert("保留2位小数：" + 1000.003.toFixed(2));   
            alert("保留1位小数：" + 1000.08.toFixed(1));   
            alert("保留1位小数：" + 1000.04.toFixed(1));   
            alert("保留1位小数：" + 1000.05.toFixed(1));   
               
            //科学计数   
            alert(3.1415.toExponential(2));   
            alert(3.1455.toExponential(2));   
            alert(3.1445.toExponential(2));   
            alert(3.1465.toExponential(2));   
            alert(3.1665.toExponential(1));   
            //精确到n位，不含n位   
            alert("精确到小数点第2位" + 3.1415.toPrecision(2));   
            alert("精确到小数点第3位" + 3.1465.toPrecision(3));   
            alert("精确到小数点第2位" + 3.1415.toPrecision(2));   
            alert("精确到小数点第2位" + 3.1455.toPrecision(2));   
            alert("精确到小数点第5位" + 3.141592679287.toPrecision(5));   
        </script>