Promise.all returning empty objects

Your .then(responses => responses.map(url => url.json())) resolves to an array of Promises, so you need to call Promise.all again if you want to wait for all to resolve:

Promise.all(promiseURLs)
  .then(responses => Promise.all(responses.map(url => url.json())))
  .then(dataArr => console.log(dataArr));

Or, you might consider using just one Promise.all, and having each URL fetch and the json, that way some items aren't idle in the middle of script execution:

const allMovieURLs = [trending, topRated, nowPlaying, upcoming];
const promiseURLs = allMovieURLs.map(url => fetch(url).then(res => res.json()));
Promise.all(promiseURLs)
  .then(dataArr => console.log(dataArr));

try doing it this way

const promiseURLs = allMovieURLs.map(url => fetch(url).then(res => res.json()));
Promise.all(promiseURLs)
  .then(responses => responses.forEach(response => { console.log(response)})