trying to await a loop

Question

I am trying to get data from database I have an array in which collection of id are present and i try to get data from a database for each id and then send to a client if try something like this:-

router.get('/getcart1', async (req, res) => {
  const email = req.body.email;`enter code here`
  const data = await cart1.find({ email: email });
  const id = data[0].id;

  let details = await id.map(async (e) => {
    console.log('start');
    console.log(e);
    let data = await books.find({ _id: e });
    console.log('end');
    return data;
  });
  res.json({ data: details });
});

the execution is start e start e end end ans when we send data details it show empty object i want all details.Inside a loop i have data but outside it show empty object

what is the value of data[0].id? You are treating it as an array by doing id.map but is it an array? — Always Learning
– Always Learning, Commented Apr 29, 2020 at 18:15
async functions return a promise. you can't use it like that. you can use await Promise.all(id.map ... ) — user120242
– user120242, Commented Apr 29, 2020 at 18:16
You cannot await an array of promises, you can only await a promise for an array. You're missing a Promise.all call. — Bergi
– Bergi, Commented Apr 29, 2020 at 18:17
actually there's definitely something else wrong with the code. Always Learning is probably right. JSON.stringify(await [Promise,Promise ... ]) should not return an empty object. Or maybe he meant [{},{} ...] as an empty object — user120242
– user120242, Commented Apr 29, 2020 at 18:26

Poul Kruijt · Accepted Answer · 2020-04-29 18:23:19Z

2

You are trying to await an array of Promises, that's not going to work, you will need a Promise.all around this:

let details = await Promise.all(id.map(async (e) => {
  console.log('start');
  console.log(e);
  let data = await books.find({ _id: e });
  console.log('end');
  return data;
}));

answered Apr 29, 2020 at 18:23

Poul Kruijt

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