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JavaScript AJAX Basics Programming AJAX Check for the correct ready state

Posted by Roberto Nieves
Roberto Nieves
9,902 Points

How can I use a DOM element's innerHTML property to set the HTML inside the sidebar div to the server's response?

I really don't understand what is meant by using the (DOM element's innerHTML property to set the HTML inside the sidebar div to the server's response). I thought I did it here.

app.js 
var xhr = new XMLHttpRequest();

xhr.onreadystatechange = function () {
    if (xhr.readyState === 4) {

      if(xhr.status === 4) {
      }

    }

  document.getElementById('sidebar').innerHTML="";


  };


xhr.open('GET', 'sidebar.html');
xhr.send();
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>AJAX with JavaScript</title>
  <script src="app.js"></script>
</head>
<body>
  <div id="main">
    <h1>AJAX!</h1>
  </div>
  <div id="sidebar"></div>
</body>
</html>