js获取字符串的字节长度

    //获得输入框中字符长度
    function getLength(val) {  
        var str = new String(val);  
        var bytesCount = 0;  
        for (var i = 0 ,n = str.length; i < n; i++) {  
            var c = str.charCodeAt(i);  
            if ((c >= 0x0001 && c <= 0x007e) || (0xff60<=c && c<=0xff9f)) {  
                bytesCount += 1;  
            } else {  
                bytesCount += 2;  
            }  
        }  
        return bytesCount;  
    }  

var str="你好"


getLength(str)

输出：4