difference between Model.find and Query.prototype.find()

Question

What is the difference between Model.find() and Query.prototype.find() in Mongoose? They both seem to do the same thing, return a Query instance. Is there any difference between them at all? Should I use one vs the other? My apologies if questions seem too simple. I'm not new to programming but new to JavaScript.

Answer 1

From the queries documentation, we know:

Mongoose models provide several static helper functions for CRUD operations. Each of these functions returns a mongoose Query object.

Model.find() method is just a wrapper for Query.prototype.find() method. These methods like Model.deleteOne(), Model.find() that are often used on the Model encapsulate several method calls on the query object, which is more convenient to use

Model.find() source code, see 7.1.1/lib/model.js#L2045

Model.find = function find(conditions, projection, options) {
  _checkContext(this, 'find');
  if (typeof arguments[0] === 'function' || typeof arguments[1] === 'function' || typeof arguments[2] === 'function' || typeof arguments[3] === 'function') {
    throw new MongooseError('Model.find() no longer accepts a callback');
  }

  const mq = new this.Query({}, {}, this, this.$__collection);
  mq.select(projection);
  mq.setOptions(options);

  return mq.find(conditions);
};

this.Query is the subclass of the Query class, see 7.1.1/lib/model.js#L4620

const Query = require('./query');
// ...

model.Query = function() {
  Query.apply(this, arguments);
};
Object.setPrototypeOf(model.Query.prototype, Query.prototype);

How does the inheritance work? See Pseudoclassical inheritance using Object.setPrototypeOf()

It creates a query instance and calls Query.prototype.select() and Query.prototype.setOptions() to set the projection and options for query. In the end, call Query.prototype.find() method.