JS通過身份證号碼擷取出生年月日

getBirthdayFromIdCard : function(idCard) {  
        var birthday = "";  
        if(idCard != null && idCard != ""){  
            if(idCard.length == 15){  
                birthday = "19"+idCard.substr(6,6);  
            } else if(idCard.length == 18){  
                birthday = idCard.substr(6,8); 
                //擷取性别
                if (parseInt(idCard.substr(16, 1)) % 2 == 1) {
                	$("#gender").val("male");
                } else {
                    $("#gender").val("female");
                } 
            }  
            birthday = birthday.replace(/(.{4})(.{2})/,"$1-$2-");  
        }  
          
        return birthday;  
      },