async.js.callbacks.js

var apiRoot = "https://jsonplaceholder.typicode.com/";
var currentUserCode = "[email protected]";

function fetchCurrentUser(cb) {
  $.ajax({url: apiRoot + "users", 
      complete: function(result) {
        if (result.status === 200) {
          var users = result.responseJSON;
          var currentUser = users
            .filter(user => user.email === currentUserCode)
            .pop(currentUser);
          cb(currentUser);
        } else {
          console.log('Error during loading');
        }
      }
  });
}

function fetchUserPosts(userId, cb) {
  $.ajax({url: apiRoot + "posts?userId=" + userId, 
      complete: function(result) {
        if (result.status === 200) {
          cb(result.responseJSON);
        } else {
          console.log('Error during loading');
        }
      }
  });
}

function fetchCommentsForPost(postId, cb) {
  $.ajax({url: apiRoot + "comments?postId=" + postId, 
      complete: function(result) {
        if (result.status === 200) {
          cb(result.responseJSON);
        } else {
          console.log('Error during loading');
        }
      }
  });
}

function flow() {
  fetchCurrentUser(function (currentUser) {
    fetchUserPosts(currentUser.id, function (posts) {
      for(var i = 0; i < posts.length; i++) {
        fetchCommentsForPost(post.id, function (comments) {
          console.log(comments);
        });
      }
    });
  })
}