I'm trying to make an API call but the customizeObj is empty in last then.

userRouter.get("/getusers", (req, apiRes) => {
  let users;
  var customizeObj = [];
  User.find()
    .then((res) => {
      users = res;
    })
    .then(() => {
      users.forEach(async (user) => {
        let event = null;
        event = await Event.findById(user.eventID);
        let year = event.date.getFullYear();
        let month =
          event.date.getMonth()   1 < 10
            ? "0"   event.date.getMonth()   1
            : event.date.getMonth()   1;
        let day =
          event.date.getDate() < 10
            ? "0"   event.date.getDate()
            : event.date.getDate();

        customizeObj.push({
          firstName: user.firstName,
          lastName: user.lastName,
          phoneNumber: user.phoneNumber,
          zipCode: user.zipCode,
          type: event.type,
          location: event.location,
          date: new Date(`${year}-${month}-${day}`),
        });
        console.log(customizeObj); // Not empty
      });
      console.log(customizeObj); // Empty
    })
    .then(() => {
      console.log(customizeObj); // Empty
      apiRes.send(customizeObj) // Sends emprty array
    })
    .catch((err) => console.log(err));
});

can please anyone help me with that? I don't know why it's empty

CodePudding user response：

Based on express and mongoose - this should work as per the above details provided.

userRouter.get("/getusers", (req, res) => {
  try{
    let customizeObj = [];
    //get users and lean
    const users = await User.find().lean();
    if(!users.length){
      //should return empty if users don't exist.
      return res.send(customizeObj); 
    }
    //loop over users.
    for(let i = 0 ; i < users.length ; i  ){
      //get event of user by users[i].eventID.
      let event = await Event.findById(users[i].eventID).lean();
      //if event exists you create the customized object, if doesn't exist again no element will be pushed to customizeObj array.
      if(event){
        let year = event.date.getFullYear();
        let month =
        event.date.getMonth()   1 < 10
          ? "0"   event.date.getMonth()   1
          : event.date.getMonth()   1;
        let day =
        event.date.getDate() < 10
          ? "0"   event.date.getDate()
          : event.date.getDate();
        customizeObj.push({
            firstName: users[i].firstName,
            lastName: users[i].lastName,
            phoneNumber: users[i].phoneNumber,
            zipCode: users[i].zipCode,
            type: event.type,
            location: event.location,
            date: new Date(`${year}-${month}-${day}`),
          });
      }
    }
    res.send(customizeObj);
  } catch(error){
    console.log('error in api',error);
    res.status(500).send({message: 'unknown error', error});
  }
});

Also, you should be creating a ref to events model and use populate('event') to get events in a single query instead of querying in a loop.

CodePudding user response：

The reason for customizeObj to be empty is probably the fact that it hasn't been filled yet. The second .then function where you iterate over users does not return a promise so the next then is executed immediately, it does not wait for the forEach loop to finish.

I have simplyfied your code to only use async await instead of mixing it with Promises(.then)

I believe it's much easier to read and the code should be self explanatory.

userRouter.get("/getusers", async (req, res) => {
    let users;
    let customizeObj = [];

    try {
        // use exec for a better stack trace
        let users = User.find({}, 'eventID').exec();
        // get all events in a single query
        let events = await Event.find({ _id: { $in: users.map(u => u.eventID) }}).exec();

        users.forEach((user) => {
            let event = events.find(ev => ev._id === user.eventID);
            let year = event.date.getFullYear();
            let month = event.date.getMonth()   1 < 10 ? "0"   event.date.getMonth()   1 : event.date.getMonth()   1;
            let day = event.date.getDate() < 10 ? "0"   event.date.getDate() : event.date.getDate();

            customizeObj.push({
                firstName: user.firstName,
                lastName: user.lastName,
                phoneNumber: user.phoneNumber,
                zipCode: user.zipCode,
                type: event.type,
                location: event.location,
                date: new Date(`${year}-${month}-${day}`),
            });
        });

        res.json(customizeObj);
    } catch(e){
        res.json([]);
    }
});