js获取长度，根据编码获取长度

    dataLen:function(str){
        var realLength = 0, len = str.length, charCode = -1;
        for(var i = 0; i < len; i++){
            charCode = str.charCodeAt(i);
            if(charCode >= 0 && charCode <= 128)
                realLength += 1;
            else
                realLength += 2;
        }
        return realLength;
    },

js获取长度