title: Uncaught TypeError: Cannot read property 'nextSibling' of undefined
body: <p>Here is piece of code i am getting an error in the console, can anyone point out where i am doing it wrong ? thanks in advance.</p>
  
  <pre><code>var intervalID = setInterval(function() {
      // every 4 seconds execute following
      var visibleWord = document.getElementsByClassName('visible')[0],
      nextWord = visibleWord.nextSibling;
  
      // check if nextSibling is textnode (whitespace) - if so get next next sibling. 
      if (nextWord.nodeType == 3) nextWord = nextWord.nextSibling;
  
      // if there is a next node 
      if (!(nextWord == null)) {
          visibleWord.setAttribute('class', 'hidden');
          nextWord.setAttribute('class', 'visible');
      } else {
          clearInterval(intervalID);
      }
  }, 4000)
  </code></pre>