Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript Asynchronous Programming with JavaScript Asynchronous JavaScript with Callbacks Implement a Callback

Cheryl Oliver
Cheryl Oliver
21,676 Points

Cant get the files to work in MAMP

I am trying to get this work in MAMP but none of the changes I make seem to do anything.

const astrosUrl = 'http://api.open-notify.org/astros.json';
const wikiUrl = 'https://en.wikipedia.org/api/rest_v1/page/summary/';
const peopleList = document.getElementById('people');
const btn = document.querySelector('button');

// Make an AJAX request
function getJSON(url, callback) {
  const xhr = new XMLHttpRequest();
  xhr.open('GET', url);
  xhr.onload = () => {
    if(xhr.status === 200) {
      let data = JSON.parse(xhr.responseText);
      return callback(data);

// Generate the markup for each profile
function generateHTML(data) {
  const section = document.createElement('section');
  section.innerHTML = `
    <img src=${data.thumbnail.source}>

btn.addEventListener('click', (event) => {
  getJSON(astrosUrl, (json) => {
    json.people.map( person => {
      getJSON(wikiUrl + person.name, generateHTML);


So you can see that I have put a console.log("data") in the addeventlistener function but nothing is appearing in the console. The astronauts are showing up on the page, 4 out of the 6 are working and then I am getting an error for 2 saying that the data.thumbnail.source is undefined.

Am I doing something silly? I am very confused!

1 Answer

charlie g
charlie g
12,417 Points

Hi Cheryl! Check this, I had the same problem.

Cheryl Oliver
Cheryl Oliver
21,676 Points

Thanks Charlie, i had a look through those answers and picked the best solution for me. The mamp issue I was having was just a caching problem luckily so thats all fixed now as well :)