title: Change the :before selector from javascript
body: <p>How to change the :before content of #abc style from javascript ?</p>
  
  <pre><code>&lt;script&gt;
  document.getElementById('abc').style.content='-';
  &lt;/script&gt;
  
  &lt;style&gt;
  #abc:before{content:"+";}
  &lt;/style&gt;
  </code></pre>