Getting value of checkboxes from listcards

I am developing an app in which I am making use of listcards to categorize sections in the app. All listcards have checkboxes and select boxes associated to a particular category. The issue is, When I click submit, I need to submit values of checkboxes in addition to the category they belong to preferably in a json format. The issue is, when ever I try to save the values I get “undefined” for all checboxes. I’m really stuck on this issue.