README.md

Using Mongoose pre middleware to systematically hash a User's password

const myuser = new User({
  email: 'jdoe@hotmail.fr',
  password: 'blacky123'
})

myuser.save()
  .then(jdoe => {
    console.log(jdoe.password) // $2b$10$nOUIs5kJ7naTuTFkBy1veuK0kSxUFXfuaOKdOKf9xYT0KKIGSJwFa
  })
  .catch(console.error)

user.js

const userSchema = new Schema({
  email: String,
  password: String
});

userSchema.pre('save', function (next) {
  if (!this.isModified('password')) return next(); // only if password has been modified (or is new)
  
  this.password = bcrypt.hashSync(this.password, 10);
  next();
});
userSchema.methods.comparePassword = function (pass, cb) {
  bcrypt.compare(pass, this.password, cb);
};

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

cf. https://mongoosejs.com/docs/middleware.html#pre