title: Form Id can't recognise addEventListener
body: <p>How do I solve the error <code>cannot read property of 'addEventListener' of null</code> ? when I add this code,<code>document.getElementById("myForm").addEventListener("submit", SaveBookmark)</code> in my JS file</p>
  
  <pre><code> &lt;form id="myForm"&gt;
        &lt;input type="text" id="siteName" size="75%" placeholder="Twitter"&gt;&lt;tr&gt;
        &lt;input type="text" placeholder="Website URL" size="75%" id="siteName"&gt;&lt;br&gt;
        &lt;button type="button" id="submitBtn"&gt;Submit&lt;/button&gt;
   &lt;/form&gt;
  </code></pre>