方法一：使用正则表达式，代码如下：

function getByteLen(val) {
            var len = 0;
            for (var i = 0; i < val.length; i++) {
                 var a = val.charAt(i);
                 if (a.match(/[\u4e00-\u9fa5]/)) 
                {
                    len += 2;
                }
                else
                {
                    len += 1;
                }
            }
            return len;
        }

方法二：使用字符unicode判断：方法如下：

function getByteLen(val) {
            var len = 0;
            for (var i = 0; i < val.length; i++) {
               var length = val.charCodeAt(i);
               if(length>=0&&length<=128)
                {
                    len += 1;
                }
                else
                {
                    len += 2;
                }
            }
            return len;
        }