急救!!!!!高手告诉下

6.3 身份证的验证 
      function isIdCardNo(num) 
      { 
        if (isNaN(num)) {alert("输入的不是数字！"); return false;} 
        var len = num.length, re;  
        if (len == 15) 
          re = new RegExp(/^(\d{6})()?(\d{2})(\d{2})(\d{2})(\d{3})$/); 
        else if (len == 18) 
          re = new RegExp(/^(\d{6})()?(\d{4})(\d{2})(\d{2})(\d{3})(\d)$/); 
        else {alert("输入的数字位数不对！"); return false;} 
        var a = num.match(re); 
        if (a != null) 
        { 
          if (len==15) 
          { 
            var D = new Date("19"+a[3]+"/"+a[4]+"/"+a[5]); 
            var B = D.getYear()==a[3]&&(D.getMonth()+1)==a[4]&&
D.getDate()==a[5]; 
          } 
          else 
          { 
            var D = new Date(a[3]+"/"+a[4]+"/"+a[5]); 
            var B = D.getFullYear()==a[3]&&(D.getMonth()+1)==a[4]&&
D.getDate()==a[5]; 
          } 
          if (!B) {alert("输入的身份证号 "+ a[0] +" 里出生日期不对！"); return false;} 
        } 
        return true; 
      }