I tried to run this but it seems that it always show the error with Chrome Console. Is there any lines you need to put in importmap.rb, or how to do this with importmap?

Uncaught TypeError: Failed to resolve module specifier "@fullcalendar/core". Relative references must start with either "/", "./", or "../".

With libraries like fullcalendar, I think importmaps often gets in the way more than it actually helps. The problem with fullcalendar, even once you get past this error, is that it internally references main.css which will then lead to the error

Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "text/css". 
Strict MIME type checking is enforced for module scripts per HTML spec.

If your project requires something like FullCalendar or any JS library that includes and references CSS files, it may be better to use esbuild via jsbundling-rails

Regardless, if you want to experiment with this, you can pin fullcalendar with something like

bin/importmap pin @fullcalendar/core

Great ep, Dave: thank you

I am almost done following this wonderful video, but I am lost on how I create custom name for the record in rails.  My end goal is to create 4-5 buttons and then name the reservation (or appointment) as the text of the button.  But when I do the params I can manually set the name, but cannot figure out where to name it in the code

body: JSON.stringify({ reservation: { start_time: info.event.start, end_time: info.event.end, name: "test" } })

Thanks for the help and great video

This is very helpful but was wondering if you could do a further video on how to use this with a multi tenancy / multi model app. For example, each user should have their own calendar so others can book times with them. How does this work?