contrived example of working with mongoose populate

handler.js

const { Post, Author } = require('./models/post.schema')
const { Poem, User } = require('./models/poem.schema')

// Then for the post, you can run a mongoose populate like so...
const getPosts = async (req, res) => await Post.find({}).populate('author')

// Then for the poem, you want to run a mongoose populate like so...
const getPoems = async (req, res) => await Poem.find({}).populate({
  path: 'author',
  model: 'User'
})

module.exports = {
  getPosts,
  getPoems
}

poem.schema.js

const mongoose = require("mongoose");
const Schema = mongoose.Schema;

// If you had a Peom schema like this
const poemSchema = new Schema({
  title: String,
  body: String,
  author: {
    type: Schema.Types.ObjectId,
    ref: 'User'
  }
}, { timestamp: true })

const Poem = mongoose.model('Poem', poemSchema)

// And a User schema like so... 
const userSchema = new Schema({
  name: String,
  username: String,
  password: String,
  post: [
    {
      type: Schema.Types.ObjectId,
      ref: 'Post'
    }
  ]
}, { timestamp: true })

const User = mongoose.model('User', userSchema)

module.exports = { Poem, User }

post.schema.js

/*
* How to work with mongoose populate
*/

const mongoose = require("mongoose");
const Schema = mongoose.Schema;

// Here's your Post schema
const postSchema = new Schema({
  title: String,
  body: String,
  author: {
    type: Schema.Types.ObjectId,
    ref: 'Author'
  }
}, { timestamp: true })

const Post = mongoose.model('Post', postSchema)

// Here's your Author schema
const authorSchema = new Schema({
  name: String,
  username: String,
  password: String,
  post: [
    {
      type: Schema.Types.ObjectId,
      ref: 'Post'
    }
  ]
}, { timestamp: true })

const Author = mongoose.model('Author', authorSchema)

module.exports = { Post, Author }