How to use promise to avoid callback hell? [duplicate]

Answer 1

The advantage of using promises is you can chain them, so your code can be reduced to:

let post, comments;
Posts.findOne({id: id}).exec().then(_post => {
    post = _post;
    return Comments.find({id: post.id}).exec();
  }).then(_comments => {
    comments = _comments;
    return Links.find({id: post.id}).exec();
  }).then(links => res.json({post, comment, links}))
  .catch(error => res.error(error.message));

you would notice that I needed only a single catch block.