Check out example codes for "detect mouse in bottom of screen + unity". It will help you in understanding the concepts better.

Code Example 1

//Quick and dirty
private void Update()
{
	Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);

  if (mousePos.y < 0)
  {
      Debug.Log("Mouse in bottom");
  }
}

Learn ReactJs, React Native from akashmittal.com