Js 扩展

计算字符串的字节长度
String.prototype.len = function () {
    return this.replace(/[^x00-xff]/g, 'xx').length;
};
alert(t.Calendar.len());

//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;  
        }

 4.00

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;  
        }