title: Set data attribute on div with js
body: <p>I've got a bunch of div.textBox that I want to apply data attribute to it.</p>
  
  <p>Here's what I want to end up with : </p>
  
  <pre><code>&lt;div class="text" data-stellar-ratio="2"&gt;
  </code></pre>
  
  <p>I've tried :</p>
  
  <pre><code>document.getElementByClassName('text').dataset.stellar.ratio = "2";
  </code></pre>
  
  <p>But it's not working...</p>
  
  <p>Help!</p>