Mongoose remove document with references - node.js

Question

I have two Schemas, eventSchema and personSchema as shown below:
var mongoose = require('mongoose')
, Schema = mongoose.Schema
var eventSchema = Schema({
title : String,
location : String,
startDate : Date,
endDate : Date
});
var personSchema = Schema({
firstname: String,
lastname: String,
email: String,
dob: Date,
city: String,
eventsAttended: [{ type: Schema.Types.ObjectId, ref: 'Event' }]
});
var Event = mongoose.model('Event', eventSchema);
var Person = mongoose.model('Person', personSchema);
How can I remove all eventsAttended from a deleted Person?
For example, if I remove a Person then I expect that all events assigned to that Person will be removed.
This is my code:
Person.findOneAndRemove({_id: req.body._id}, (err, response) => {
// remove the events assigned to this person
})

Answer 1

With mongoose you can use pre and post middleware on your schemas:
personSchema.post('remove', removeLinkedDocuments);
Then in the removeLinkedDocuments callback, you can remove all linked documents:
function removeLinkedDocuments(doc) {
// doc will be the removed Person document
Event.remove({_id: { $in: doc.eventsAttended }})
}
Note the middleware is only called for the following methods (refer to the linked documentation for details):
count
find
findOne
findOneAndRemove
findOneAndUpdate
update
To remove the documents 'manually' in your callback, you might do
Person.findOneAndRemove({_id: req.body._id}, (err, response) => {
// note that if you have populated the Event documents to
// the person documents, you have to extract the id from the
// req.body.eventsAttended object
Event.remove({_id: { $in: req.body.eventsAttended }}, (err, res) => {
...
})
})