fullcalander dateClick()

[SariMorgenshtern]

I'm using the fullcalander plugin in a Laravel app with Filament.
The board is shown correctly to me.
I want to add a click event on a day view in a calendar, I want to use JS code to listen for the click.
This is my code:

document.addEventListener('DOMContentLoaded', function () {
 var calendarEl = document.getElementById('calendar');
 var calendar = new FullCalendar.Calendar(calendarEl, {
 selectable: true,
 headerToolbar: {
 left: 'prev, next today',
 center: 'title',
 right: 'dayGridMonth,timeGridWeek,timeGridDay'
 },
 dateClick: function (info) {
 alert('clicked ' + info.dateStr);
 },
 });

 calendar.render();
});

Indeed, when loading, it enters the function, but throws an error like this:

ReferenceError: FullCalendar is not defined

On this line:

 var calendar = new FullCalendar.Calendar(calendarEl, {

What could be my problem?