i\'m using jQuery fullcalendar on a ReactJs component.
i have a on the render method
and on componentD
I was having the same issue after upgrading fullCalendar, took me a bit to figure out because for almost a year everything has been working fine and I had upgraded fullCalendar in the past without any issues, for some reason I had to include moment.js in the page I was using the fullCalendar on, see I run an MVC site and previously the master page (_layout.cshtml) was referencing moment.js, not sure right now why that doesn't work anymore, just as a test I added a reference to moment in the actual page I use fullCalendar and the undefindundefined went away and so did another issue I was having with events.
In my case the fix was:
@Scripts.Render("~/bundles/dates")
in your case it may just be: