How to rename path in response for populate
You can do this by virtual populate, introduced in mongoose version 4.5 . For that you need to define a virtual field in mongoose schema.
var GallerySchema = new mongoose.Schema({ name: String, objectId: { type: mongoose.Schema.Types.ObjectId },});GallerySchema.virtual('user', { ref: 'User', localField: 'objectId', foreignField: '_id' });Ans when you run find query, just populate it with user.
Gallry.find({_id: galleryId}).populate('user','firstName lastName').exec(function(error, gallery) { console.log(error); console.log(gallery);;});Above code is not tested in program, there may be typos, You can get more details about mongoose virtual populate on below link