似乎无法弄清楚为什么我的 promise 阵列不工作

Question

I'm working on a project where at one point, I run a series of promises and then push their results (in the.then() portion) to an array. The issue is that, although the promise itself is providing a result value, nothing is actually being pushed to the array itself. Below is the create function in my code where I'm using Promise.all() to run a series of processes on an array made of promises called newJoinsPromiseArray .

 export const create = (req, res, next) => { const newJoinsPromiseArray = []; //This will be an array of the new joins that we are adding for (const worker of req.body.workers){ const newJoinElement = new JoinTable(null, req.body.contact_id, worker.value) //We use value here since it's in the form that multi-select gave us newJoinElement.save().then((result) => { newJoinsPromiseArray.push(JoinTable.findByID(result[0].insertId)) }).catch(err => res.json({message: err})) } Promise.all(newJoinsPromiseArray).then((values) => {console.log(values)}) }

So whenever I console.log(newJoinsPromiseArray), it just prints [] . I've tried this also by just running the JoinTable.findByID function on each element then pushing what it returns to the array, although I think that's the same thing.

Below are my functions for save and findByID:

 save(){ /* The purpose of this function is to save a new element to the database. */ return db.execute(`INSERT INTO workercontacts (contact_id, worker_id) VALUES(?, ?)`, [this.contact_id, this.worker_id]); }

 static findByID(element_id){ // Will give us a specific element based on the id return db.execute('SELECT * FROM workerContacts WHERE workerContacts.id =?', [element_id]); }

I'm using a MySQL database which I don't think has anything to do with this issue but I thought I'd add that information just in case.

Edit:

Adding on to this, this was my new attempt at making this work, which it still didn't

 export const create = async (req, res, next) => { const newJoinsPromiseArray = []; //This will be an array of the new joins that we are adding for (const worker of req.body.workers){ const newJoinElement = new JoinTable(null, req.body.contact_id, worker.value) //We use value here since it's in the form that multi-select gave us try{ const savedResult = await newJoinElement.save(); const joinElementByID = await JoinTable.findByID(savedResult[0].insertId); newJoinsPromiseArray.concat(joinElementByID); } catch (e){ res.json({message: e}) } } console.log(newJoinsPromiseArray) }

I'm still lost unfortunately but thank you for all of your help thusfar.

Answer 1

You should be pushing the Promise s into the array.

newJoinsPromiseArray.push(newJoinElement.save().then(result => JoinTable.findByID(result[0].insertId));

Alternatively, you could make the function async and use await on each of the save operations in the loop.

Answer 2

I figured it out thanks to @Unmitigated: I just changed my create function to be this:

 export const create = (req, res, next) => { const newJoinsPromiseArray = []; for (const worker of req.body.workers){ const newJoinElement = new JoinTable(null, req.body.contact_id, worker.value) //We use value here since it's in the form that multi-select gave us newJoinsPromiseArray.push(newJoinElement.save().then(result => JoinTable.findByID(result[0].insertId))) } Promise.all(newJoinsPromiseArray).then((values) => res.json(values.map(val => val[0]).flat())) }