title: Get value of attribute in CSS
body: <p>I have this HTML code:</p>
  
  <pre><code>&lt;div data-width="70"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>I want to set it's width in CSS equal to the value of data-width attribute, e.g. something like this:</p>
  
  <pre><code>div {
      width: [data-width];
  }
  </code></pre>
  
  <p>I saw this was done somewhere, but I can't remember it. Thanks.</p>