Here's is the Code !!

//Step 2 
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/myDatabase', {
  useNewUrlParser: true,
  useUnifiedTopology: true,
  useCreateIndex: true
}).then(() => console.log('Connected to MongoDB'))
.catch(err => console.error('Failed to connect to MongoDB', err));

//Step 3
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'Connection error:'));
db.once('open', () => {
  console.log('Connected to MongoDB');
});

//Step 4
const { Schema, model } = mongoose;
const userSchema = new Schema({
  username: { type: String, required: true, unique: true },
  email: { type: String, required: true, unique: true },
  password: { type: String, required: true },
});
const User = model('User', userSchema);

//Step 5

//create 
const newUser = new User({ username: 'johnDoe', email: 'john@example.com', password: 'password123' });
newUser.save().then(user => console.log('User created:', user)).catch(err => console.error('Error creating user:', err));

//Read
User.find({}).then(users => console.log('Users:', users)).catch(err => console.error('Error fetching users:', err));

//Update
User.updateOne({ username: 'johnDoe' }, { email: 'newEmail@example.com' }).then(result => console.log('User updated:', result)).catch(err => console.error('Error updating user:', err));

//Delete
User.deleteOne({ username: 'johnDoe' }).then(result => console.log('User deleted:', result)).catch(err => console.error('Error deleting user:', err));