How do I FILTER returned data between two dates from mongodb using an aggregation : match, lookup and project?

Question

I would like to get all Notifications between a start and end date that are related to a Register when I pass in a userId.

Register Schema

Answer 1

Your solution looks almost right, provided that dateStart and dateStart are actually Date objects and not Strings.

Your Try 2 was incomplete I'm not sure it uses the $lookup from Try 1 or not. If so you have to make sure the output of $lookup is the same as input of $filter. So you should change as in $lookup to match input of $filter

{
  $lookup: {
    from: "notifications",
    localField: "accessToken",
    foreignField: "accessToken",
    as: "items" // here
  }

}

Alternative Solution

I'm not sure what you want as output. If you only need array of notifications without the user object, you can try the following.

[{
  $match: { userId: mongoose.Types.ObjectId(userId) }
}, {
  $lookup: {
    from: "notifications",
    localField: "accessToken", // don't forget to index register.accessToken
    foreignField: "accessToken", // don't forget to index notification.accessToken
    as: "notifications"
  }
}, {
  $unwind: "$notifications"
}, {
  $match: { 
    dateCreated: { $gte: dateStart, $lte: dateEnd } // dateStart, dateEnd should be Date objects
  }
}, { // optional, move notifications to top lvel
  $replaceRoot: { root: '$notifications' }
}]