populate method in mongoose code example

Example 1: mongoose populate

Story.
  findOne({ title: /casino royale/i }).
  populate('author', 'name'). // only return the Persons name
  exec(function (err, story) {
    if (err) return handleError(err);

    console.log('The author is %s', story.author.name);
    // prints "The author is Ian Fleming"

    console.log('The authors age is %s', story.author.age);
    // prints "The authors age is null'
  });

Example 2: mongoose create populate response

let user = await User.create({ ... })
user = await user.populate('company').execPopulate()

Example 3: mongoose populate()

// populates a single object
User.findById(id, function (err, user) {
  const opts = [
    { path: 'company', match: { x: 1 }, select: 'name' },
    { path: 'notes', options: { limit: 10 }, model: 'override' }
  ];

  User.populate(user, opts, function (err, user) {
    console.log(user);
  });
});

// populates an array of objects
User.find(match, function (err, users) {
  const opts = [{ path: 'company', match: { x: 1 }, select: 'name' }];

  const promise = User.populate(users, opts);
  promise.then(console.log).end();
})

// imagine a Weapon model exists with two saved documents:
//   { _id: 389, name: 'whip' }
//   { _id: 8921, name: 'boomerang' }
// and this schema:
// new Schema({
//   name: String,
//   weapon: { type: ObjectId, ref: 'Weapon' }
// });

const user = { name: 'Indiana Jones', weapon: 389 };
Weapon.populate(user, { path: 'weapon', model: 'Weapon' }, function (err, user) {
  console.log(user.weapon.name); // whip
})

// populate many plain objects
const users = [{ name: 'Indiana Jones', weapon: 389 }]
users.push({ name: 'Batman', weapon: 8921 })
Weapon.populate(users, { path: 'weapon' }, function (err, users) {
  users.forEach(function (user) {
    console.log('%s uses a %s', users.name, user.weapon.name)
    // Indiana Jones uses a whip
    // Batman uses a boomerang
  });
});
// Note that we didn't need to specify the Weapon model because
// it is in the schema's ref

Example 4: how to use mongoose populate

{  _id: 59ab1c92ea84486fb4ba9f28,  username: JD,  posts: [    "59ab1b43ea84486fb4ba9ef0",    "59ab1b43ea84486fb4ba9ef1"  ]}

Example 5: how to use mongoose populate

{   _id: 59ab1c92ea84486fb4ba9f28,  username: 'JD',  posts:    [       {         _id: 59ab1b43ea84486fb4ba9ef0,        content: "Is it dark out?"      },{        _id: 59ab1b43ea84486fb4ba9ef1,        content: "Hey anyone got a cup of sugar?"      }    ]  }

Example 6: mongoose populate

//EXAMPLE TWO

const mongoose = require('mongoose')
const shortid = require('shortid')

/**
 * @description setup database connection
 */
mongoose
  .connect('mongodb://localhost:27017/mongoose', {
    useFindAndModify: false,
    useUnifiedTopology: true,
    useNewUrlParser: true
  })
  .then(() => console.log('Connected'))
  .catch(() => console.log('Not Connected'))

/**
 * @description course mongoose schema
 */

const CourseSchema = new mongoose.Schema(
  {
    userId: { type: mongoose.Types.ObjectId },
    course: []
  },
  { timestamps: true }
)

const Course = mongoose.model('Course', CourseSchema, 'Course')

/**
 * @description user mongoose schema
 */

const UserSchema = new mongoose.Schema(
  {
    fullName: {
      type: String,
      trim: true,
      required: true
    },
    courseId: {
      type: String,
      ref: 'Course',
      default: shortid.generate
    }
  },
  { timestamps: true }
)

UserSchema.post('save', async function (doc, next) {
  if (doc) {
    await Course.create({ userId: doc._id })
    next()
  }
})

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

/**
 * @description register user account
 */

async function registerAccount() {
  const userData = new User({ fullName: 'john doe' })
  await userData.save()

  console.log('register successfuly')
  process.exit(0)
}
registerAccount()

/**
 * @description buy video course
 */

async function buyCourse() {
  const user = await User.findOne({ fullName: 'john doe' })

  const course = await Course.updateOne(
    { userId: user._id },
    {
      $push: {
        course: {
          $each: [
            { name: 'react for beginner', price: 95000 },
            { name: 'vue for beginner', price: 85000 },
            { name: 'angular for beginner', price: 75000 }
          ]
        }
      }
    }
  )

  console.log('sucessfuly to buy course')
  process.exit(0)
}
// buyCourse()

/**
 * @description results all course after buy course
 */

async function resultsCourse() {
  const user = await User.findOne({ fullName: 'john doe' })

  const courseResult = await Course.findOne({ userId: user._id })
    .populate({
      path: 'userId',
      select: 'course firstName lastName'
    })
    .lean()

  console.log({
    fullname: user.fullName,
    courses: courseResult.course
  })
  process.exit(0)
}
// resultsCourse()