Fullcalendar.io CSS not working in rails 6 app

Here is what works for me:

I use webpacker with Rails 6.0.3.

1. '/app/javascript/packs/application.js':

require("fullcalendar/fullcalendar.js")

2. '/app/javascript/fullcalender/fullcalendar.js' (This is a custom folder working together with the require in 1):

import { Calendar } from "@fullcalendar/core";
import dayGridPlugin from "@fullcalendar/daygrid";


document.addEventListener('turbolinks:load', function() {
  var calendarEl = document.getElementById('calendar');

  var calendar = new Calendar(calendarEl, {
    plugins: [ dayGridPlugin ],
    height: "parent",

  });

  calendar.render();
});

3. '/app/assets/stylesheets/custom.scss':

@import '@fullcalendar/core/main.css';
@import '@fullcalendar/daygrid/main.css';

4. 'html.erb'

<section class="section">
   <div id="calendar"></div>
</section>

Depending on whether you're using Webpack or if you're just using a CSS compressor, you might not be able to just import the CSS by referencing the package.

For example @import '@fullcalendar/core/main.css'; references the package @fullcalendar/core in your node_modules folder, but some CSS processors aren't configured to look in node_modules.

If they are, then a simple path like this will work:

@import 'node_modules/@fullcalendar/core/main.css';
@import 'node_modules/@fullcalendar/daygrid/main.css';
@import 'node_modules/@fullcalendar/list/main.css';

If they are not, you'll need to use a relative path:

@import '../node_modules/@fullcalendar/core/main.css';
@import '../node_modules/@fullcalendar/daygrid/main.css';
@import '../node_modules/@fullcalendar/list/main.css';

You may have to alter the path in the example above for your specific setup. The path to node_modules should be relative to your CSS files.