title: What does this JavaScript object array expression {}[] mean?
body: <p>I am trying to understand the following JavaScript code I have found (and actually use) in Masonry:</p>
  
  <pre><code>var docElem = document.documentElement;
  var transitionProp = typeof docElem.style.transition == 'string' ?
      'transition' : 'WebkitTransition';
  var transitionEndEvent = {
    WebkitTransition: 'webkitTransitionEnd',
    transition: 'transitionend'
  }[ transitionProp ];
  </code></pre>
  
  <p>Does the expression {}[] mean, that the transitionProp variable is added to transitionEndEvent object? 
  And is the Expression typeof docElem.style.transition someway of finding out if css transition is supported?</p>
  
  <p>Thanks for your help!</p>