title: change the flex properties of a DOM object in JavaScript
body: <p>I have a very simple div in my DOM. I want to add a style property to this div element using JavaScript.</p>
  <p>my element is selected like so:</p>
  <pre><code>const firstBlock = document.getElementById('box1')
  </code></pre>
  <p>just for the sake of testing things out I kept it super simple and just tried this:</p>
  <pre><code>firstBlock.style.display= &quot;flex : 4&quot;
  </code></pre>
  <p>but this does not add anything to the class linked to the element...</p>
  <p>any idea how to do this very simply?</p>
  <p>and I just tried:</p>
  <pre><code>firstBlock.style.flexGrow= 6
  </code></pre>
  <p>which adds the flex-grow property of 6, but it's not working on the screen...</p>