title: Transition effect is not working properly
body: <p>Transition doesn't work, I want to achieve the smooth effect on scroll. I'm using the JS script below, the script is working. However, CSS transition is not.</p>
  <p>Any help is appreciated!</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>window.onscroll = function() {
    scrollFunction()
  };
  
  function scrollFunction() {
    if (document.body.scrollTop &gt; 550 || document.documentElement.scrollTop &gt; 550) {
      document.getElementById("header").style.height = "70px";
      document.getElementById('classic-logo').style.display = "none";
      document.getElementById('minifyed-logo').style.display = "block";
  
    } else {
      document.getElementById("header").style.height = "100px";
      document.getElementById('minifyed-logo').style.display = "none";
      document.getElementById('classic-logo').style.display = "block";
    }
  }</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#header {
    position: fixed;
    width: 100%;
    height: 100px;
    transition: 0.3s;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;header id="header"&gt;
    &lt;!-- Content --&gt;
  &lt;/header&gt;</code></pre>
  </div>
  </div>
  </p>