title: How to get notified when an element is made visible on the page?
body: <p>It's clear to me how to check if an element is visible on the page, by using the functions explained <a href="https://stackoverflow.com/questions/19669786/check-if-element-is-visible-in-dom">on this question</a>.</p>
  
  <pre><code>//Where el is the DOM element you'd like to test for visibility
  function isHidden(el) {
      return (el.offsetParent === null)
  }
  </code></pre>
  
  <p>Or</p>
  
  <pre><code>//Where el is the DOM element you'd like to test for visibility
  function isHidden(el) {
      var style = window.getComputedStyle(el);
      return (style.display === 'none')
  }
  </code></pre>
  
  <p>But to avoid pooling for the <code>isHidden(el)</code> function, I'd like to be notified when a given element is made visible in the DOM (with pure JS, no jQuery or other frameworks).</p>
  
  <p>In theory <a href="https://developer.mozilla.org/en/docs/Web/API/MutationObserver" rel="nofollow noreferrer">mutation observers</a> could be used, but I need a solution for IE10+ browsers.</p>
  
  <p>Any ideas?</p>