making relation to another mongo document using mongoose methods

index.js

// this is a file in the root folder

const User = require("./models/user.js");

const main = async () => {
	// to show tasks saved by a particular user
	
	const user = await User.findById("5e54b46f3022d70b2ceaf2e5")
// 	console.log(user.tasks)    --> without virtual (returns undefined, as tasks ain't a field)
	
	user.populate("tasks").execPopulate()
	console.log(user.tasks) // returns all tasks
}

main()

user.js

// this is the user model root >> models >> user.js

const mongoose = require("mongoose")

const userSchema = new mongoose.Schema({
  email: {
    type: String,
    required: true
  },
  password: {
    type: String,
    required: true
  }
})

userSchema.virtual("tasks", {
  ref: "User",
  localField: "_id",
  foreignField: "owner"
})


const User = new mongoose.model("User", userSchema)
module.exports = User