title: Get div's margin value?
body: <p>I'm trying to figure out if it's possible to read a div's margins with JavaScript if those margins are set in <code>external css</code> file. 
  So far I am able to read div's margin data when it is written as an inline style (not in CSS file but inside HTML):</p>
  
  <pre><code>(function() {
    var banner = document.getElementById('banner');
    var move = document.getElementById('box');
  
    banner.onclick = function() {
  
      alert(move.style.marginLeft);
  
    };
  })();
  </code></pre>
  
  <p>Here is JSFiddle:
  <a href="https://jsfiddle.net/b0kaLk1f/" rel="nofollow">https://jsfiddle.net/b0kaLk1f/</a></p>
  
  <p>It works well but just remove  <code>style="margin-left: 500px"</code> and it will stop working.  I'd like to read CSS data from <code>style.css</code> file rather than from inline styles.</p>