title: What is the difference between screenX/Y, clientX/Y and pageX/Y?
body: <p>What is the difference between <code>screenX</code>/<code>Y</code>, <code>clientX</code>/<code>Y</code> and <code>pageX</code>/<code>Y</code>?</p>
  
  <p>Also for iPad Safari, are the calculations similar as on desktop—OR there is some difference because of viewport?</p>
  
  <p>It would be great if you could point me to an example.</p>