How can I project a field that is inside an object in mongodb

Question

I'm using "sample_mflix" database provided by mongo atlas and mongodb vs code extension to practice. My code looks like this so far:

use('sample_mflix');

db.movies.aggregate([
  {
    $lookup: {
      from: 'comments',
      localField: '_id',
      foreignField: 'movie_id',
      as: 'comments'
    },
  },
  {$unwind: '$comments'},
  {  
    $project:{
      comments:'$comments',
      _id:0 
    }
  },
    {  
    $project:{
       name:'$comments.name',
       email:'$comments.email',
       date:'$comments.date',
    }
  },
])

And this is the result I get from it:

[
  {
    "name": "Taylor Scott",
    "email": "[email protected]",
    "date": {
      "$date": "1970-11-15T05:54:02Z"
    }
  },
  {
    "name": "Jaqen H'ghar",
    "email": "[email protected]",
    "date": {
      "$date": "1981-11-08T04:32:25Z"
    }
  },
  {
    "name": "Yara Greyjoy",
    "email": "[email protected]",
    "date": {
      "$date": "2012-11-26T11:00:57Z"
    }
  }
.
.
.]

As you can see, the date field is an object in this document, but I want to bring with $project only the string value of the date which is in the $date field, like this:

  {
    "name": "Yara Greyjoy",
    "email": "[email protected]",
    "date": "2012-11-26T11:00:57Z"
  }

How can I achieve it ?

Answer 1

Use $toString

db.collection.aggregate([
  {
    $set: {
      date: {
        $toString: "$date"
      }
    }
  }
])

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