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Mongodb – Node mongo group by specific field

I have a response like this:

 "data": [
    {
      "_id": "6664a8f2f233916895656171",
      "workout_plan_id": "6664a5a089450f21a8dd69dc",
      "day": "Monday",
      "exercise_id": "66643259d020507ed008b16d",
      "reps": 15,
      "sets": 3,
      "created_on": "2024-06-08T18:54:16.287Z",
      "updated_on": "2024-06-08T18:54:16.287Z",
      "__v": 0
    },
    {
      "_id": "6664aa55ce325f608597f5e8",
      "workout_plan_id": "6664a5a089450f21a8dd69dc",
      "day": "Monday",
      "exercise_id": "66643259d020507ed008b16d",
      "reps": 15,
      "sets": 3,
      "created_on": "2024-06-08T18:59:34.019Z",
      "updated_on": "2024-06-08T18:59:34.019Z",
      "__v": 0
    },
    {
      "_id": "6664aa89ce325f608597f5eb",
      "workout_plan_id": "6664a5a089450f21a8dd69dc",
      "day": "Tuesday",
      "exercise_id": "66643259d020507ed008b187",
      "reps": 15,
      "sets": 3,
      "created_on": "2024-06-08T18:59:34.019Z",
      "updated_on": "2024-06-08T18:59:34.019Z",
      "__v": 0
    }
 ]

I want to group the response on the basis of day like this:

    monday:[],
    tuesday:[],

and so on…

Tags:

2

Answers


  1. 0

    You can achieve the grouping of documents by the weekday directly using MongoDB’s aggregation framework. Here’s how you can do it:

    Group by day and accumulate exercises in an array.
    Use $project to transform each grouped result into a key-value pair.
    Use $group again to accumulate these key-value pairs into an array.
    Convert the array to an object using $arrayToObject.

     db.yourCollectionName.aggregate([
  {
    $group: {
      _id: "$day",
      exercises: { $push: "$$ROOT" }
    }
  },
  {
    $project: {
      _id: 0,
      k: "$_id",
      v: "$exercises"
    }
  },
  {
    $group: {
      _id: null,
      kvPairs: { $push: { k: { $toLower: "$k" }, v: "$v" } }
    }
  },
  {
    $project: {
      _id: 0,
      result: { $arrayToObject: "$kvPairs" }
    }
  }
])

    The output looks like:

    {
  result: {
    monday: [],
    tuesday: []
  }
}
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  2. 0

    Option 1:

    If doing this in the database you can use an aggregation like so:

    db.collection.aggregate([
  {
    $group: {
      _id: "$day",
      docs: {
        $push: "$$ROOT"
      }
    }
  },
  {
    $project: {
      arr: [
        {
          "k": "$_id",
          "v": "$docs"
        }
      ]
    }
  },
  {
    $project: {
      docs: {
        $arrayToObject: "$arr"
      }
    }
  },
  {
    $replaceWith: "$docs"
  }
])

    See HERE for a working example.

    Option 2:

    If doing this on the client after your response is received you can use the new Object.groupBy():

    const response = {
   "data": [
      {
        "_id": "6664a8f2f233916895656171",
        "workout_plan_id": "6664a5a089450f21a8dd69dc",
        "day": "Monday",
        "exercise_id": "66643259d020507ed008b16d",
        "reps": 15,
        "sets": 3,
        "created_on": "2024-06-08T18:54:16.287Z",
        "updated_on": "2024-06-08T18:54:16.287Z",
        "__v": 0
      },
      {
        "_id": "6664aa55ce325f608597f5e8",
        "workout_plan_id": "6664a5a089450f21a8dd69dc",
        "day": "Monday",
        "exercise_id": "66643259d020507ed008b16d",
        "reps": 15,
        "sets": 3,
        "created_on": "2024-06-08T18:59:34.019Z",
        "updated_on": "2024-06-08T18:59:34.019Z",
        "__v": 0
      },
      {
        "_id": "6664aa89ce325f608597f5eb",
        "workout_plan_id": "6664a5a089450f21a8dd69dc",
        "day": "Tuesday",
        "exercise_id": "66643259d020507ed008b187",
        "reps": 15,
        "sets": 3,
        "created_on": "2024-06-08T18:59:34.019Z",
        "updated_on": "2024-06-08T18:59:34.019Z",
        "__v": 0
      }
   ]
};
const groupByDay = Object.groupBy(response.data, ({ day }) => day);
console.log(groupByDay);

    For compatability of Object.groupBy see Caniuse.

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