title: Get element by tag name and class name
body: <p>(in vanilla JavaScript) I was wondering if the was an easy way to do something like </p>
  
  <pre><code>x = document.getElementsByTagName('span') &amp;&amp; getElementsByClassName('null');
  </code></pre>
  
  <p>To return all 'span' elements that have the class name 'null'? </p>
  
  <p>I thought it might have been something like: </p>
  
  <pre><code>x = document.getElementsByTagName('span'); 
  x = x.getElementsByClassName('null');
  // or     
  x = document.getElementsByTagName('span').getElementsByClassName('null');
  </code></pre>
  
  <p>But that didn't seem to work out. </p>
  
  <p>Is this possible or will I have to iterate through x popping anything that returns false for .class='null'?</p>
  
  <p>Thanks. </p>