如何从嵌套异步 function 返回数据

Question

async getSettlementByUser(email): Promise<any> {
    let listofTerminalId = [];
    // Get current user
    let user = await this.userModel.findOne({ email: email });
    // get list of sn
    let tpeIndexes = user.bindedSn.map((item) => item);
    //list des tpes binded to current user
    let tpe = tpeIndexes.map(async (index) => {
      let list = await this.tpeModel.find({ sn: index });
      // console.log('liste des tpes', list);
      let terminalId = list.map((item) => item.terminalId);
      // console.log('terminalId', ...terminalId);
      listofTerminalId.push(...terminalId);

      console.log('listofTerminalId', listofTerminalId);
      return await listofTerminalId.map(async (item) => {
        return await this.modelSettlement
          .find({ terminalID: item })
          .then((res) => res)
          .catch((err) => console.log(err));
      });
      // console.log('settlement', settlement);
      // return settlement;
    });

    let promiseValue = await Promise.all(tpe);
    console.log('promiseValue', promiseValue);
    // // return promiseValue;
    // return tpe;
  }

OUTPUT

promiseValue [   [ Promise { <pending> } ],   [ Promise { <pending> }, Promise { <pending> } ],   [
    Promise { <pending> },
    Promise { <pending> },
    Promise { <pending> }   ] ]

I used Promise.all() to handle this nested async still get this result so How can I resolve this problem and why it shows this error

Answer 1

You use Promise.all only on the outer layer of the nesting, not on the inner array of promises. You would also need to do

return Promise.all(listofTerminalId.map(async (item) => {
//     ^^^^^^^^^^^
  return this.modelSettlement
    .find({ terminalID: item })
    .catch((err) => console.log(err));
}));

---

However, given the listofTerminalId.push(...terminalId) , it looks like you actually don't want any nesting. You may just want to

async getSettlementByUser(email): Promise<any> {
  // Get current user
  const user = await this.userModel.findOne({ email: email });

  // list des tpes binded to current user
  const tpes = await Promise.all(user.bindedSn.map(async (index) => {
    const list = await this.tpeModel.find({ sn: index });
    // console.log('liste des tpes', list);
    return list.map((item) => item.terminalId);
  }));
  const listofTerminalId = tpes.flat();
  console.log('listofTerminalId', listofTerminalId);

  const settlements = await Promise.all(listofTerminalId.map((item) => {
    return this.modelSettlement.find({ terminalID: item })
  }));
  console.log('settlements', settlements);
}

Answer 2

You need to pass an array of promises to Promise.all method that means you should neither await the promises nor .then them before passing them to Promise.all .

So it might look like this:

async getSettlementByUser(email): Promise<any> {
    let listofTerminalId = [];
    let user = await this.userModel.findOne({ email: email });
    let tpeIndexes = user.bindedSn.map((item) => item);

    let tpe = tpeIndexes.map(async (index) => {
        let list = await this.tpeModel.find({ sn: index });
        let terminalId = list.map((item) => item.terminalId);
        listofTerminalId.push(...terminalId);
  
        return listofTerminalId.map((item) => {
            return this.modelSettlement
              .find({ terminalID: item })
        });
    });

    let promiseValue = await Promise.all(tpe)
    console.log('promiseValue', promiseValue);
}