how to recover from duplicate key in mongoose + express

Question

I've created a signup form using mongoose and express 3

Its possible the user already exists with that username, in which case I get an err.code 11000 (duplicate key). How should I handle existing users?

This is what I'm doing now....but I'm not sure checking error code is best way:

  user.save(function(err){
    if ( err ) {
      console.log(err);
      console.log(err.code);

      //duplicate key
      if ( err.code == 11000 ) {
        req.flash('error', 'User already exists');
        res.redirect('/signup');
        return;
      }
    }

    res.locals.user = user;
    req.session.user = user;
    //res.locals.session = req.session;
    res.redirect('/');
  });

Is there a better way of doing this?

Answer 1

Try this:

user.save(function(err){
  if ( err && err.code !== 11000 ) {
    console.log(err);
    console.log(err.code);
    res.send('Another error showed up');
    return;
  }

  //duplicate key
  if ( err && err.code === 11000 ) {
    req.flash('error', 'User already exists');
    res.redirect('/signup');
    return;
  }

  res.locals.user = user;
  req.session.user = user;
  //res.locals.session = req.session;
  res.redirect('/');
});

You won't fill the error log this way.

Answer 2

I have not tried this yet, but this is what I'm thinking will avoid causing an error:

//look for existing user first
user.findOne({ username: req.body.username }, function(err, user) {
  if ( err ) throw err;

  //existing user found, stop registration
  if ( user ) {
      res.flash('error', "That user already exists");
      res.redirect('/signup');
      return;
  }

  //create new user
  var user = new User({ username: req.body.username });

  user.save(function(err){
   if ( err ) throw err;
      res.flash('info', "Your account has been created");
      res.redirect('/account');
  });
});