title: Mongoose right promise rejection handling
body: <p>I'm bit fighting with promise pattern in nodeJS</p>
  
  <p>I'm looking for user in db and then saving new entity with user reference, but when user is not in db, I should return rejection, but I'm not sure how to do it properly.</p>
  
  <p>is there way how to do it more nicely? </p>
  
  <p>btw: sorry, coffeescript :-[</p>
  
  <pre><code>User.findOne({'fbId':userData.me.id}).exec().then((doc)-&gt;
    if !doc? then return new Promise (resolve,reject)-&gt;reject(404)
  
    video = new Video({
      user:doc
      state: "queue"
      createdAt: new Date()
    })
  
    video.save().exec()
  )
  </code></pre>