Mongo shell: is it possible to add a custom function to cursor?

Question

In the command line tool mongosh, is it possible to add a custom function and I can use it this way: >db.somecollection.myCustomFunc()

Answer 1

Based on your comments, I have no idea what you are looking for.

But purely based on your question, the solution is this one:

Object.defineProperty(db.getSiblingDB('so').getCollection("somecollection"), 'giveMeFive', {
   enumerable: true,
   writable: false,
   configurable: false,
   value: () => {return 5}
});

and the just use it

use so
db.somecollection.giveMeFive()
5

Or another example:

Object.defineProperty(db.getSiblingDB('so').getCollection("somecollection"), 'insertTwo', {
   enumerable: true,
   writable: false,
   configurable: true,
   value: (x) => { 
      db.getSiblingDB('so').getCollection("somecollection").insertMany([x, x]); 
      return 'OK'; 
   }
});

use so
db.somecollection.insertTwo({ val: 3 })
OK

db.somecollection.find()
[
  { _id: ObjectId("63ceb12b2545bff4a24f2872"), val: 3 },
  { _id: ObjectId("63ceb12b2545bff4a24f2873"), val: 3 }
]

But as written in my comment, when you restart the shell then your property gets deleted.