I am creating a node.js app with Express and socket.io. I want to use SASS and I see there is a npm package for it, what I don't understand is how do I link between the SASS npm and the app and make it parse the SASS?

UPDATE: I used SASS middleware https://github.com/andrew/node-sass installed it and included it the following way:

  sass = require('node-sass');


app.configure(function(){
  app.set('port', process.env.PORT || 3000);

  /* other stuff */

  sass.middleware({
    src: __dirname + '/public/stylesheets/sass',
    dest: __dirname + '/public/stylesheets',
    debug: true
  });
});

But it still doesn't work

You need to use the sass middleware, for example this one.

Quoting from docs:

var server = connect.createServer(
   sass.middleware({
       src: __dirname
       , dest: __dirname + '/public'
       , debug: true
    }),
   connect.static(__dirname + '/public')
);

in case of using express, just add:

 app.use(
     sass.middleware({
         src: __dirname + '/sass', //where the sass files are 
         dest: __dirname + '/public', //where css should go
         debug: true // obvious
     })
 );

to your app.configure() call.

Of course on production systems it's a better idea to precompile sass to css.

update

In the example above the middleware will look for sass files in __dirname + '/sass/css'. Also by default it looks for files with .scss extension. There doesn't seem to be an option to change the extension.