Each then () must return a value or throw when using Promises

Question

I have several async methods that I need to wait for completion before I return from the request. I use Promises, but I get an error all the time:

Each then() should return a value or throw // promise/always-return

Why is this happening? This is my code:

router.get('/account', function(req, res) {
  var id = req.user.uid
  var myProfile = {}
  var profilePromise = new Promise(function(resolve, reject) {
    var userRef = firebase.db.collection('users').doc(id)
    userRef.get()
      .then(doc => { // Error occurs on this line
        if (doc.exists) {
          var profile = doc.data()
          profile.id = doc.id
          myProfile = profile
          resolve()
        } else {
          reject(Error("Profile doesn't exist"))
        }
      })
      .catch(error => {
        reject(error)
      })
  })
  // More promises further on, which I wait for
})

Answer 1

Just avoid Promisethe antipattern constructor ! If you do not call resolve, but return a value, you will have something up to return. The method thenshould be used for chaining, and not just for subscription :

outer.get('/account', function(req, res) {
  var id = req.user.uid
  var userRef = firebase.db.collection('users').doc(id)
  var profilePromise = userRef.get().then(doc => {
    if (doc.exists) {
      var profile = doc.data()
      profile.id = doc.id
      return profile // I assume you don't want to return undefined
//    ^^^^^^
    } else {
      throw new Error("Profile doesn't exist")
//    ^^^^^
    }
  })
  // More promises further on, which I wait for:
  // profilePromise.then(myProfile => { … });
})

Answer 2

resolve() -, resolve(myProfile) ,

Answer 3

firebase.db.collection('users').doc(id) promise , , firebase node -js.

promises, , Promises .

, , .

,

          router.get('/account', function(req, res) {

            var id = req.user.uid;
            var myProfile = {};

            var userRef = firebase.db.collection('users').doc(id)

            userRef.get()
            .then(doc =>  {

                if (!doc || !doc.exists) {
                   throw new Error("Profile doesn't exist")
                }

                var profile = doc.data();
                profile.id = doc.id;
                myProfile = profile;

               return myProfile;

            })
            .catch(error => {
              console.log('error', error);
            })

          })

Promise.all, promises, .

Promise.all(iterable) , , promises promises. , .

:

  var promise1 =  new Promise((resolve, reject) => {
    setTimeout(resolve, 100, 'foo1');
  });
  var promise2 =  new Promise((resolve, reject) => {
    setTimeout(resolve, 100, 'foo2');
  });
  var promise3 =  new Promise((resolve, reject) => {
    setTimeout(resolve, 100, 'foo3');
  });

  Promise.all([promise1, promise2, promise3])
  .then(result =>  console.log(result))
  //result [foo1, foo2, foo3] 

, !