How to populate nested document in MongoDB.

Recently I run into a situation where I needed to fetch nested mongodb document data and wasted my 1 hour. If you are facing the same this is for you.

Here is the stackoverflow - Populate nested array in mongoose

I used this query -

public courseListRead(): Promise<ICourse[]> {
    return this.courseModel.find().sort({
      index: 1
    }).populate('instructor').populate({
      path: 'categories',
      populate: {
        path: 'posts',
        model: 'CourseCategoryPost'
      }
    }).exec();
  }

To populate nested documents you have to use .populate() method like above.

I'm very beginner at MongoDB.

Thanks.