lesson09/getElemenById.html

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Change URL</title>
    <script type="text/javascript">
      
      function changeLink() {
        let changedLink = 0;
        if (changedLink == 0) {
          //get Element with ID 'ChangeURL' in HTML to assign value
          document.getElementById('ChangeURL').innerHTML = 'CIW Certified';
          document.getElementById('ChangeURL').href = 'http://ciwcertified.com';
          //we also can add attribute by using get Element ID
          document.getElementById('ChangeURL').target='_blank';
          changedLink++;
          console.log(changedLink);
        } else {
          document.getElementById('ChangeURL').innerHTML = 
            'Microsoft';
          document.getElementById('ChangeURL').href =
            'http://microsoft.com';
          document.getElementById('ChangeURL').target='_blank';
          changedLink--;
          console.log(changedLink);
        }
      }
    </script>
  </head>
  <body>
    <h2>CIW JavaScript Specialist</h2>
    <h3>Change URL</h3>
    <a id="ChangeURL"
      href="http://www.microsoft.com">Microsoft</a><br>
    <input type="button" value="Change Link" onClick="changeLink()">
  </body>
</html>