title: Setting width and height as a percentage in JavaScript
body: <p>Here is my JavaScript code:</p>
  
  <pre><code>a.width = a.width ? a.width : 640;
  a.height = a.height ? a.height : 360;
  </code></pre>
  
  <p>How can I make the 640px and 360px percentages instead? I want them both to be 70% of the windows size.</p>