Mongoose User Password middleware

encryptPassword.js

import bcrypt from 'bcrypt'
import Promise from 'bluebird'

const Constants = {
  PASSWORD_MAX_LENGTH: 64,
  PASSWORD_SALT_FACTOR: 10
}
const hash = Promise.promisify(bcrypt.hash)
const genSalt = Promise.promisify(bcrypt.genSalt)
const compare = Promise.promisify(bcrypt.compare)

export function comparePassword(password, hashedPassword) {
  return compare(password, hashedPassword)
}

export default function encryptPassword(password) {
  if (password.length > Constants.PASSWORD_MAX_LENGTH) {
    password = password.substr(0, Constants.PASSWORD_MAX_LENGTH)
  }

  return genSalt(Constants.PASSWORD_SALT_FACTOR).then(salt => {
    return hash(password, salt)
  })
}

UserSchema.js

import encryptPassword, {comparePassword} from './encryptPassword'

/**
 * Password hash middleware.
 */
UserSchema.pre('save', function (next) {
  const user = this;
  if (!user.isModified('password')) { return next(); }
  
  encryptPassword(user.password).then(hash => {
    user.password = hash
    next()
  })
  .catch(next)
});

/**
 * Instance method for validating user's password.
 */
UserSchema.methods = {
  comparePassword(plainPassword) {
    return comparePassword(plainPassword, this.password)
  }
}