Get some objects from array of objects in a document (mongoose)

Question

I want to get some objects from array of objects in a mongodb document my document looks something like this

{
    movieDetails: {
        movieId: 333,
        movieName: "movie",
    },
    Dates: [
        {
            Date: " 01/07/2021",
            TheaterId: 12,
            Is3D: "false",
        },
        {
            Date: " 09/07/2021",
            TheaterId: 13,
            Is3D: "false",
        },
        {
            Date: " 03/07/2021",
            TheaterId: 12,
            Is3D: "false",
        }
    ]
}

I want to get only the objects where the movieId is equal to 333 and TheaterId is 12 my result should look like this

 [
        {
            Date: " 01/07/2021",
            TheaterId: 12,
            Is3D: "false",
        },
        {
            Date: " 03/07/2021",
            TheaterId: 12,
            Is3D: "false",
        }
 ]

I tried this

const dates = await Movie.find("movieDetails.movieId": 333).select({ Dates: {$elemMatch: {TheaterId: 12}}});

But it returns only the first object if anyone can help me with this I will be very grateful

J.F. · Accepted Answer · 2021-08-26 21:02:42Z

According to $elemMatch docs:

The $elemMatch operator limits the contents of an field from the query results to contain only the first element matching the $elemMatch condition.

So you can use this aggregation pipeline using $filter into a $project stage like this:

Movie.aggregate([
  {
    "$match": {
      "movieDetails.movieId": 333
    }
  },
  {
    "$project": {
      "movieDetails": 1,
      "Dates": {
        "$filter": {
          "input": "$Dates",
          "as": "d",
          "cond": {
            "$eq": [
              "$$d.TheaterId",
              12
            ]
          }
        }
      }
    }
  }
])

Example here

Or this another pipeline (I prefer using $filter)

Movie.aggregate([
  {
    "$match": {
      "movieDetails.movieId": 333
    }
  },
  {
    "$unwind": "$Dates"
  },
  {
    "$match": {
      "Dates.TheaterId": 12
    }
  },
  {
    "$group": {
      "_id": "$_id",
      "movieDetails": {
        "$first": "$movieDetails"
      },
      "Dates": {
        "$push": "$Dates"
      }
    }
  }
])

Example here

Andrew L · Accepted Answer · 2021-08-26 20:38:16Z

0

I would suggest taking a look at the doc for .find() since it seems you are using it incorrectly.

One way you can achieve this is to use .find() to find the movie with the ID you want, then .filter() the Dates from that object to return just the ones with your TheaterId

here is an example

const movies = [{
  movieDetails: {
    movieId: 333,
    movieName: "movie",
  },
  Dates: [{
      Date: " 01/07/2021",
      TheaterId: 12,
      Is3D: "false",
    },
    {
      Date: " 09/07/2021",
      TheaterId: 13,
      Is3D: "false",
    },
    {
      Date: " 03/07/2021",
      TheaterId: 12,
      Is3D: "false",
    }
  ]
}]

function findMovieTimesByTheater(movieID, theaterID) {
  const movie = movies.find(movie => movie.movieDetails.movieId === movieID);

  if (typeof movie === "undefined") {
    console.log(`movieID: ${movieID} not found`);
    return [];
  }

  return movie.Dates.filter(date => date.TheaterId === theaterID);
}

const times = findMovieTimesByTheater(333, 12);
console.log(times);

answered Aug 26, 2021 at 20:38

Andrew L

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1 Comment

haim brandesdorfer Over a year ago

my question was about document in mongoose not about objects in js apparently I did not explain my question well I edited the question it seems to me that now it is clearer

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