difference between 'done' and 'next' in node.js callbacks

Question

in the passport [configure authentication] documentation, it has a rather scary-looking function that uses the mysterious function \"done.\'

passport.use(new         


        

Answer 1

Let's back up because I think you may have some confusion.

Express is a web application framework. It's responsible for directing users to resources, in a very broad sense.

Passport is a authentication framework. It's responsible for making sure that users are allowed to access said resources.

In both frameworks there is a idea of middleware. Middleware is basically generalized control flow. For example, in some Express framework you could say:

1. Make sure parameter x is valid when requesting route /user/:x

   • if valid, then next() --> which means go to next middleware function()

2. Make sure the user has a session, etc

3. And when all middleware has been executed, then we execute the application

For example,

router.get('/', function(req, res) { // when the '/' route is requested
    res.render('index', { title: 'Express' }); // send index.html
});

In Passport, they also use the idea of middleware, however, instead of next(), they use done() and it's a little more complex. See this page for more info
http://toon.io/understanding-passportjs-authentication-flow/