In order to call this method, you'd have to access it via event.nativeEvent.stopImmediatePropagation(): https://developer.mozilla.org/en-US/docs/Web/API/Event/stopImmediatePropagation
It'd be awesome if this was supported on event itself. I did see a prior issue for this, but it was for a use case that sIP wasn't required for.
For a specific use case: if you want to kill hover events for touch input, onTouchStart will trigger onMouseOver and stopImmediatePropagation cancels that internal cascade.