Loop of promises does not return JSON in Node.js

Question

I have an array with the Events to be searched, to check if there is another one on the same day and time.

The code below returns me the existing events without problem, but only on the console.log. I must return to the Front and for now I’m not succeeding.

In short, my loop does not return the json I need to the front.

const searchEvent = async event => {
      const response = await Event.findOne({
        where: {
          [Op.or]: [
            {
              start: { [Op.between]: [event.start, event.end] },
            },
            {
              end: { [Op.between]: [event.start, event.end] },
            },
          ],
          room_id: event.room_id,
        },
      });
      return response;
    };

    const loadEvents = arrayOfEventsWithDateIniAndDateEnd.map(
      async event =>
        await searchEvent(event).then(result => console.log(result))
    );

    return res.json(loadEvents);

Return of Insomnia:

Answer 1

The problem is here:

const loadEvents = arrayOfEventsWithDateIniAndDateEnd.map(
  async event =>
    await searchEvent(event).then(result => console.log(result))
  );

return res.json(loadEvents);

Note that you are mapping an array of values into an array of promises. Remember that asynchronous functions at all times will return a Promise.

Therefore, you need a means to ensure that all the promises of the mapped array are resolved before passing them to the method res.json.

To do this, just use the function Promise.all, that awaits the resolution of all the promises of the array, returning a new array with the values of each resolution.

Thus:

const loadEvents = arrayOfEventsWithDateIniAndDateEnd.map(
  async event =>
    await searchEvent(event)
  );

try {
  const resolvedValues = await Promise.all(loadEvents);
  return res.json(resolvedValues);
} catch (err) {
  return res.status(500).json({
    status: 'err',
    error: err.message
  });
}

Do not forget to treat for any mistakes. If one of the promises fails, Promise.all will also reject. Learn more in the documentation.