How to find data from nested array in Mongoose?

Question

I have two ids: publisherID and BookID.

My mongoose database looks like:

Now the question is: I want to find userId where the publishderId is 59l55llopd3W1FuosGgN and the bookId is G1Vfe2NwS3sy-qhT1J0g6

I've created the following function which returns the null data.

const allTheRelatedData = (publiserId, bookId) => {
    return new Promise((resolve, reject) => {
        try {
            myBookSchema
                .findOne({
                    publisherId: publisherId,
                    "books.$.bookId": bookId,
                })
                .then((data) => {
                    console.log(data);
                    resolve(data);
                })
                .catch((error) => {
                    console.log(error);
                    reject(error);
                });
        } catch (error) {
            console.log(error);
            reject(error);
        }
    });
};

When I run this code, it gives null data. Please help, I tried many solutions such as positional, match, etc. Nothing is working. Please help.

Cuong Le Ngoc · Accepted Answer · 2021-06-29 01:20:42Z

4

You can use $ projection operator to do that:

myBookSchema
  .findOne({
    publisherId: publisherId,
    "books.bookId": bookId,
  }, {
    "books.$": 1
  }
).then((data) => {...

Then you can get userId with data.books[0].userId and remember to check if data or book exists with if (data && data.books && data.books.length)...

edited Jun 29, 2021 at 1:20

answered Jun 29, 2021 at 1:18

Cuong Le Ngoc

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9 Comments

Agent K Over a year ago

Can you please tell what is 1 in the line: books.$: 1? As I don't know the index of the book.

Cuong Le Ngoc Over a year ago

It will select the first book that match "books.bookId": bookId in the condition. You can find more info in the link I provided

Agent K Over a year ago

Sorry, but this code: .findOne( { publisherId: publisherId, "books.bookId": bookId, }, { "books.$": 1 } ) is also not working.

Agent K Over a year ago

And when I replaced 1 with 0 it gave me error: MongoError: positional projection cannot be used with exclusion

Cuong Le Ngoc Over a year ago

And "books.$": 1 is for projection, not for condition.

|

im2rnado · Accepted Answer · 2021-06-28 18:32:17Z

1

Maybe this would work

const allTheRelatedData = (publiserId, bookId) => {
    return new Promise((resolve, reject) => {
        try {
            myBookSchema
                .find()
                .then((data) => {
                    const item = data.filter(i => i.publisherId === publisherId && i.books.includes(book => book.bookId === bookId))
                    if (item) {
                        console.log(item);
                        resolve(item);
                    } else {
                        console.log("Not found");
                        reject("Not found");
                })
                .catch((error) => {
                    console.log(error);
                    reject(error);
                });
        } catch (error) {
            console.log(error);
            reject(error);
        }
    });
};

answered Jun 28, 2021 at 18:32

im2rnado

915 bronze badges

1 Comment

Agent K Over a year ago

This one is not working @im2rando also getting a message data.filter is not a function.

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