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Determines if events being dragged and resized are allowed to overlap each other.

boolean / function. default: true

If false, no events are allowed to overlap. If true, all events are allowed to overlap (the default).

If given a function, the function will be called every time there is a pair of intersecting events, whether upon a user drag or resize. The function must return true if the overlap should be allowed and false otherwise. The below example allows overlapping only if both events are all-day:

var calendar = new Calendar(calendarEl, {
  events: [ /* event data here */ ]
  eventOverlap: function(stillEvent, movingEvent) {
    return stillEvent.allDay && movingEvent.allDay;

movingEvent is the event that is being dragged or resized. Its start and end dates will remain at their original values when the callback function is called. stillEvent is the event underneath the moving event.

If a timed event occurs on the same day as an all-day event, this will qualify as an intersection. This might seem confusing in the TimeGrid views because the events don’t visually intersect because the all-day slot is separate from the timed slots. But it’s still considered an overlap.

The eventOverlap setting does not differentiate between background events or normal events. It treats both types of events the same way.

If you need more granular control for which events are allowed to overlap, you can do this with each Event Source’s overlap property or with each Event Object’s overlap property. View a demo that does this.