How to pass a hashed password in a promise before posting it to the database using a Node.js server?

Question

On a node.js server I am using bcrypt to hash a password which is received by a user via a POST request and then store the hash in a database. The hashing function function takes longer to compute than creation of the saving of the hash and other parameters to the database, so I need to use a promise to executing the save after the hashing function has finished. I am using the Q library for this purpose, but I'm not sure how to do this. I am using mongoose for data modelling.

async bcrypt hashing function

var bcrypt = require('bcrypt');
  bcrypt.genSalt(10, function(err, salt) {
    bcrypt.hash(req.body.password, salt, function(err, hash) {
      // Store hash in DB
    });
  });
});

POST route

app.post('/api/users', function(req, res) {

  var newUser = new User({
    email: req.body.email,
    name: req.body.name,
    password: hash
  });

  newUser.save(function(err) {
    if(!err) {
      return res.send({ status: 'User created' });
    } else {
      if(err.name == 'ValidationError') {
        res.statusCode = 400;
        res.send({ error: 'Bad Request' });
      } else {
        res.statusCode = 500;
        res.send({ error: 'Internal Server Error' });
      }
    } 
  });
});

I would figure the population of the newUser variable and newUser.save() call would be the argument of then(), but how do I make the bcrypt hashing function issue the promise and pass the hash?

Answer 1

You could simply move your database queries, to inside the callback of the hash, so that when the hash call back is ready it would then save it.

var bcrypt = require('bcrypt');

app.post('/api/users', function(req, res) {
  bcrypt.genSalt(10, function(err, salt) {
    bcrypt.hash(req.body.password, salt, function(err, hash) {
      var newUser = new User({
        email: req.body.email,
        name: req.body.name,
        password: hash
      });

      newUser.save(function(err) {
        if(!err) {
          return res.send({ status: 'User created' });
        } else {
          if(err.name == 'ValidationError') {
            res.statusCode = 400;
            res.send({ error: 'Bad Request' });
          } else {
            res.statusCode = 500;
            res.send({ error: 'Internal Server Error' });
          }
        } 
      });
    });
  });
});

Or use the synchronous call of bcrypt.hashSync but synchronous is not good practice when trying to work with Node.

But it could be like password: bcrypt.hashSync(req.body.password, salt)

If I understand correctly what you're asking, you want to save the user, after the password is hashed?