Wsrtjtyk

I've started learning NodeJS to use it with Firebase in order to create Functions.

I'm currently stuck because I have nested forEach which must be async.

I'll try to be as understandable as possible.

I have 3 nodes:

• Terminals


• Bookings


• TerminalBookings (which is like a join table)

I have to create a function to get all the terminals with their bookings associated.

So I have to get all the terminals, for each terminal I can get all the terminalbookings associated (the node key is the terminal id and all the values are bookings id).

And then when I have all the terminalbooking, I can get the booking informations in the bookings node.

It look pretty easy to do with Sql but I can figure out how to do it with NodeJS.

Here is what I have (in this state, it's impossible to work, but it looks like what I want to do):

async function getReservationsSnapshotByTerminalId(terminalId) {

  const terminalReservationsSnap = await admin.database().ref(`/terminalBookings/${terminalId}`).once('value');

  const terminalReservations = Object.keys(terminalReservationsSnap.val());



  const reservationsSnapshot = terminalReservations.map((reservationId) => {

    return admin.database().ref(`/bookings/${reservationId}`).once('value');

  });



  return Promise.all(reservationsSnapshot);

}



exports.showTerminalsWithReservations = functions.https.onRequest(async (request, response) => {

  let terminals = ;

  try {

    const terminalsSnapshot = await admin.database().ref('/terminals/').once('value');



    terminalsSnapshot.forEach(terminalSnapshot => {

      const terminal = new Borne(terminalSnapshot.key, terminalSnapshot.val());

      const bookingsSnapshot = await getReservationsSnapshotByTerminalId(terminal.key);



      bookingsSnapshot.forEach(booking => {

        terminal.bookings.push(booking.val());

      });

      terminals.push(terminal);

    });

  } catch(error) {



  }

 });

But it can't work because of this line :

const bookingsSnapshot = await getReservationsSnapshotByTerminalId(terminal.key);

If I want to use the await, the parent forEach must by async but it's not possible.

I think that I'm not in the right way to handle this feature but I'm stuck, I don't know how to do it.

Feel free to completely rebuild this function if I'm wrong.

You can achieve that with either of following 2 ways

for await (let terminal of terminals){

   await getReservationsSnapshotByTerminalId(terminal.terminalId);

   console.log(terminalId);

}

console.log("Done");

Output:

Terminal1

Terminal2

Terminal3

Done

OR

var promise = Promise.all(terminals.map((terminal) => {

  console.log(terminal.id);

  return await getReservationsSnapshotByTerminalId(terminal.id);

}));



promise.then(() => console.log("Done"));

Again output is:

Terminal1

Terminal2

Terminal3

Done

how about this

const getReservationsSnapshotByTerminalId = (terminalId) => {

     return admin.database().ref(`/terminalBookings/${terminalId}`).once('value')

       .then(snapshot => {

          const terminalReservations = Object.keys(terminalReservationsSnap.val());

          const reservationsSnapshot = terminalReservations.map(reservationId => {

               return admin.database().ref(`/bookings/${reservationId}`).once('value');

       });

       return Promise.all(reservationsSnapshot);

     });

};



exports.showTerminalsWithReservations = functions.https.onRequest(async (request, response) => {

     let terminals = ;

     try {

        terminals = await admin.database().ref('/terminals/').once('value')

           .then(snapshot =>{

               const promises = ;

               const allTerminals = snapshot.val();

               const terminalKeys = Object.keys(allTerminals);

               const terminalsArray = terminalKeys.map(key => new Borne(key, allTerminals[key]));

               promises.push(terminalsArray);

               promises = promises.concat(terminalKeys.map(key => getReservationsSnapshotByTerminalId(key)));

               return Promises.all(promises);

           })

          .then(resultArray => {

               const terminalsArray = resultArray[0];

               terminalsArray.forEach((terminal, idx) => {

                  const bookingsSnapshot = resultArray[idx + 1];

                  bookingsSnapshot.forEach(booking => {

                      terminal.bookings.push(booking.val());

                  });

               });

               return terminalsArray;

         });





} catch(error) {



 }

});