Modify attributes in beforeCreate hook

Introduction#

We might need to modify the attributes before record is created. My use case was encrypting password when user is created.

Hooks doc is here https://docs.sequelizejs.com/en/v3/docs/hooks/#instance-hooks. It documents the way to use it with a library / function that returns a Promise. But the use case with a callback is not clearly documented.

Syntax#

beforeCreate(instance)
beforeCreate(instance, options, fn)

Example working with a library that doesn’t use Promise

function cryptPassword(password, callback) {
  bcrypt.genSalt(SALT_WORK_FACTOR, function(err, salt) {
    if (err)
      return callback(err);

    bcrypt.hash(password, salt, null, function(err, hash) {
      return callback(err, hash);
    });
  });
}

User.beforeCreate((user, options, cb) => {
  cryptPassword(user.password, (err, hash) => {
    if (err) return cb(err);

    user.password = hash;
    // invoking the finish callback is important!
    return cb(null, options);
  });    
});

Example working with a library that doesn’t use Promise

User.beforeCreate(function(user, options) {
  return hashPassword(user.password).then(function (hashedPw) {
  user.password = hashedPw;
  });
})