issue with parent checkbox value with node.js cant be read using java script

Node.js and EJS

I have a html page in node js using ejs template wherein i have main checkbox for Hobbies(x) with id hobby with checkbox check by default once the page loads .and underneath i have 5 options(a,b,c,d,e) . these sub checkbox underneath hobbies are also checked by default.

I am wondering how do i write a java script function inside node.js router so that when box is unchecked no result should get displayed in node.js console and i should be able to send data to mongodb collection.

Please note that i am able to access the checkbox with id req.body.hobbyid when selected and send this data to backend server. However when i unselect the parent checkbox i am getting that value is undefined in node.js console.

Code snippet below

if (req.body.hobby[0]) {
      console.log(a); //here x can be any value
}
if (req.body.hobby[1]) {
      console.log(b); //here y can be any value
}
if (req.body.hobby[2]) {
      console.log(c); //here x can be any value
}
if (req.body.hobby[3]) {
      console.log(d); //here y can be any value
}

// code to connect to mongodb which i am not giving here which works very well when i check the main checkbox for hobby.

I want to achieve a way wherein when main parent checkbox(here which is hobby with id hobbymain is unchecked it should store a value as "False" and set the value as "Not submitted" in db and store in some variable which i can later pick the send to backend server.

Please note that when all checkbox are checked it works perfectly fine . However if i uncheck main Hobby checkbox all children checkbox (a,b,c,d) are unchecked and it throws me exception saying invalid reference.


A Prompt reply would be helpful