PointerEvent.pointerId

The pointerId read-only property of the PointerEvent interface is an identifier assigned to a given pointer event. The identifier is unique, being different from the identifiers of all other active pointer events. Since the value may be randomly generated, it is not guaranteed to convey any particular meaning.

A number.

The following code snippet compares a previously saved pointerId with the one of the pointerdown event that was just fired.

let id; // Let's assume that this is a previously saved pointerId

target.addEventListener('pointerdown', function(event) {
  // Compare previous event's ID that was cached
  // to current event's ID and handle accordingly
  if (id === event.pointerId) process_event(event);
}, false);