title: document is not defined in NodeJS
body: <p>I am trying to build a website including HTML, CSS and JS. </p>
  
  <p>I have a HTML file and a JS file. I am trying to give the values of the HTML file to the JS file by using <code>document.getElementById();</code> but it wont work. </p>
  
  <p>This problem kinda holds me back and I am stuck because of that.</p>
  
  <pre><code>var b = document.getElementById("radioYes"); // a radio button called "yes"
  var d = document.getElementById("radioNo"); // a radio button called "no"
  var c = document.getElementById("submit1"); // submit-button
  </code></pre>
  
  <p>What can I do?</p>