npm i mongo-aggregator

There are three methods:

1. expander.expandOne(childPath, projection, [childCollectionName]) for expand simple (not array) field.

2. expander.expandMany(childPath, projection, [childCollectionName]) for expand array field.

3. expander.expandManyWithChildProjection = function (childPathName, projection, childProjection, childCollectionName) for expand array field with projection for child documents.

   A result of functions will be aggregation obj.

   Next:

   // mongoose MyModel.aggregate(aggregationObj, function(err, myModels) { ... });

   // or mongo driver db.collection('myCollection').aggregate(aggregationObj, function(err, myDocs) { ... });