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JavaScript AJAX Basics (retiring) Programming AJAX Check for the correct ready state

Posted by Bruce Mattys
Bruce Mattys
5,662 Points

Stage 2 - Programming AJAX - Challenge Task 3 of 4 - What's wrong with my code?

This is the challenge question:

Now that the server has responded with the data, you need to add it to the page. First select the div with the ID of 'sidebar'. You can select page elements with IDs like this: document.getElementById('idName');

I added the last line of code (the rest was already there):

var xhr = new XMLHttpRequest(); xhr.onreadystatechange = function() { if (xhr.readyState === 4) {} if (xhr.status === 200) {} }; xhr.open('GET', 'sidebar.html'); xhr.send(); document.getElementById('sidebar');

I get this error:

Bummer! To select the <div> tag with the 'sidebar' ID, you need to pass the ID name as a string to the getElementById method, like this: document.getElementById('sidebar')

What am I doing wrong?

app.js 
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {}
  if (xhr.status === 200) {}
};
xhr.open('GET', 'sidebar.html'); 
xhr.send();
document.getElementById('sidebar');
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>

2 Answers

Colin Bell
Colin Bell
29,679 Points
Colin Bell
Colin Bell
29,679 Points

It's asking you to select the #sidebar inside the xhr.onreadystatechange function.

Also, make sure your xhr.status conditional is inside your xhr.readyState conditional.

var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
    if (xhr.status === 200) {
      document.getElementById('sidebar');
    }
  }
};
xhr.open('GET', 'sidebar.html');
xhr.send();
Bruce Mattys
Bruce Mattys
5,662 Points

Got it -- thanks, Colin!

Jonathan Ambriz
Jonathan Ambriz
Courses Plus Student 3,902 Points

Why does it have to be nested inside the conditional instead of using &&?

John Norris
John Norris
21,145 Points
John Norris
John Norris
21,145 Points 
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
    if (xhr.readyState === 4, xhr.status === 200) {
  document.getElementById('sidebar');
  }
};
xhr.open('GET', 'sidebar.html');
xhr.send();