button

On "pointerdown", "pointerup", and "click" , this property indicates the device button whose state change caused the event to fire. -1: Neither buttons nor touch/pen contact changed since last event. 0: Left Mouse, Touch contact, Pen contact. 1: Middle Mouse. 2: Right Mouse, Pen barrel button. 3: X1 (back) Mouse 4: X2 (forward) Mouse 5: Pen eraser button