title: Check if element is visible for certain percentage on screen (viewport)?
body: <p>How can i detect if some element is visible? For better understading look at the image below.</p>
  
  <p><img src="https://i.stack.imgur.com/Ndcdz.png" alt="Screen with half-visible image"></p>
  
  <p>I want to fire event when the image is half-visible. It would be great if it would work for all browsers and devices (tablets and smartphones).</p>