while sending Promise result in api response, result is coming empty in Express js-CodePudding

Tech:- Node, Express, Mongoose

1 - In an Api, I fetched all the documents from a mongoDB collection.which gives result as data(array) 2 - In each element of data done an async operation(Promise) 3 - consoled the data, got the result as expected ** 4 - but in response.send({data}) ** giving empty objects. 5 - If there is no async in map operation, Iam getting everything perfectly

 await clientsOfSeller
      .find()
      .then(async (result) => {
        let data = result.map( async someFunction);

        Promise.all(data).then(() => {
          console.log(data);     // showing output

          res
            .status(200)
            .send({
              data,              // getting empty objects
            });
        });

      
      })

CodePudding user response：

You're adding the data variable to the response but data is simply the list of promises you created. It doesn't magically turn into a list of results after the promises resolve.

The response data gets turned into a JSON using the JSON.stringify() function. A Promise stringifies to an empty object, that's why you get empty objects in the response.

What you actually want to include in the response are the resolved results of the promises, which you get as the first argument to the callback method you pass to the .then() method of Promise.all().
Change that part of your code into this:

    Promise.all(data).then((results) => {
      console.log(results);
      res
        .status(200)
        .send({
          status: 200,
          message: "success",
          data: results,
        });
    });