Populate nested array in mongoose

Question

How can I populate "components" in the example document:

  {
    "__v": 1,
    "_id": "5252875356f64d6d28000001",
    "pages": [
      {
        "__v": 1,
        "_id": "5252875a56f64d6d28000002",
        "page": {
          "components": [
            "525287a01877a68528000001"
          ]
        }
      }
    ],
    "author": "Book Author",
    "title": "Book Title"
  }

This is my JS where I get document by Mongoose:

  Project.findById(id).populate('pages').exec(function(err, project) {
    res.json(project);
  });

Answer 1

Mongoose 4.5 support this

Project.find(query)
  .populate({ 
     path: 'pages',
     populate: {
       path: 'components',
       model: 'Component'
     } 
  })
  .exec(function(err, docs) {});

And you can join more than one deep level