title: How to change css class property with javascript?
body: <p>can someone tell me how can i change css class property by javascript?
  example:</p>
  
  <pre><code>.winner
  {
      background-color: white;
  }
  </code></pre>
  
  <p>How can I change value of class winner background-color.
  When I write:
  var some = document.querySelector("winner");
  I get button with class winner. I want this class not element of html. How can i get it?</p>