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JavaScript AJAX Basics Programming AJAX Check for the correct ready state

Posted by Michael MacKenzie
Michael MacKenzie
8,633 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
231,275 Points
Steven Parker
Steven Parker
231,275 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.