NodeJs - callback is not defined - How do I use async for password hashing?

Question

I'm fairly new to nodeJS, and I've been tasked with creating a sample registration page, and with it, my attempts at encrypting the user's password.

Here's what I came up with, used by simply passing the user's password:

function hashPassword(password) {
  var salt = crypto.randomBytes(128).toString('base64')
  var iterations = 1000;
  var hash = crypto.pbkdf2Sync(password, salt, iterations, 512, 'sha512');
  return {
    salt: salt,
    hash: hash.toString('base64'),
    iterations: iterations
  };
}

Now, I heard that it's best practice to use async on functions that may take awhile, but unfortunately I'm rather new to async on JS.

Here's what I came up with through google searches ( specifically, here ), but I neither understand it completely nor could I get it to work. Keeps saying ReferenceError: callback is not defined :

function hashPassword(password, callback) {
  var saltBytes = 128;
  var iterations = 1000;
  var hashBytes = 512
  crypto.randomBytes(saltBytes, (err, salt) => {
    if (err) {
      return callback(err);
    }

    crypto.pbkdf2(password, salt, iterations, hashBytes, 'sha512', (err, hash) => {
      if (err) {
        return callback(err);
      }

      var combined = new Buffer(hash.length + salt.length + 8);
      combined.writeUInt32BE(salt.length, 0, true);
      combined.writeUInt32BE(iterations, 4, true);

      salt.copy(combined, 8);
      hash.copy(combined, salt.length + 8);
      callback(null, combined);
    });
  });
}

As far as my limited knowledge of async goes, it's in the callback function I'm supposed to do whatever else is required (in my case, save to DB).

What did I do wrong, or what am I not getting?

Answer 1

Are you calling your function like this ?

hashPassword('password here', function (error, combined) {
  if(error) {
    // handle error
  } else {
    // do something with combined
  }
});

I think the error is because you are not sending the callback function as second parameter when you call hashPassword function

Check this gist