Error in Firebase Demo

ErrorInFbDemo.md

https://www.firebase.com/blog/2015-10-07-how-to-keep-your-data-consistent.html

function fanoutPost({ uid, followersSnaphot, post, postId }) {
  // Turn the hash of followers to an array of each id as the string
  var followers = Object.keys(followersSnaphot.val());
  var fanoutObj = {};
  // write to each follower's timeline
  // Correction: I think it needs something like this:
  followers.forEach((key) => fanoutObj['/timeline/' + key + '/' + postId] = post);
  return fanoutObj;  
}