Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript AJAX Basics Programming AJAX Check for the correct ready state

Michael MacKenzie
Michael MacKenzie
7,704 Points
Posted by Michael MacKenzie
Michael MacKenzie
7,704 Points

Now use a DOM element's innerHTML property to set the HTML inside the sidebar div to the server's response.

I don't know what I'm doing wrong, but I'm fairly sure I've got it correct... or mostly correct. It has to be a typo or something I'm not seeing. This is the error I'm getting.

Bummer: There was an error with your code: TypeError: onreadystatechange handler threw exception: 'null' is not an object (evaluating 'document.getElementById('sidebar').innerHTML = xhr.responseText')

app.js 
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) { 
  }

document.getElementById('sidebar').innerHTML = xhr.responseText;
};
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>

1 Answer

Steven Parker
Steven Parker
230,069 Points
Steven Parker
Steven Parker
230,069 Points

You're right, you just have a placement issue. The line that displays the response should be inside the conditional instead of after it. Just exchange lines 4 and 6.