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 Create a callback

William Tunna
William Tunna
2,946 Points
Posted by William Tunna
William Tunna
2,946 Points

I don't understand why I'm getting a Parse error here

I'm not sure what I'm doing wrong here. The challenge is to create a onreadystatechange on line 2, with an anonymous function, but I'm getting a Parse Error

app.js 
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = () => {};
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
231,269 Points
Steven Parker
Steven Parker
231,269 Points

This course was likely developed before ES2015 syntax was in common use. Try using a conventional function expression instead of an "arrow" function.

Even in modern code, arrow functions aren't always the best choice for handlers because they don't establish a value for "this" like conventional functions do.