Mongoose populate embedded

As of Mongoose 3.6 the ability to recursively populate related documents in a query has been added. Here is an example of how you might do it:

 UserList.findById(listId)
         .populate('refUserListItems')
         .exec(function(err, doc){
             UserListItem.populate(doc.refUserListItems, {path:'refSuggestion'},
                   function(err, data){
                        console.log("User List data: %j", doc);
                        cb(null, doc);
                   }
             );     
          });           

In this case, I am populating an array of id’s in ‘refUserListItems’ with their referenced documents. The result of the query then gets passed into another populate query that references the field of the original populated document that I want to also populate – ‘refSuggestion’.

Note the second (internal) populate – this is where the magic happens. You can continue to nest these populates and tack on more and more documents until you have built your graph the way you need it.

It takes a little time to digest how this is working, but if you work through it, it makes sense.