Common Pre-Handler for ConnectJS/ExpressJS url handlers?

Question

In my ExpressJS app, several of my urls handlers have the following logic:

1. See if the user has permission to access a resource
2. If so, continue
3. Else, redirect to the main handler.

Is there a way to insert a pre-handler for certain url handlers, via ConnectJS or ExpressJS?

I know I can do it globally, for all handlers, (which I do to insert missing headers as a result from IE's broken XDR).

But, can I do this for a subset of handlers?

Answer 1

I do something like this:

lib/auth.js

exports.checkPerm = function(req, res, next){
  //do some permission checks
  if ( authorized ) {
     next();
  } else {
     res.render('/401');
     return;
  }
};

app.js

var auth = require('./lib/auth');
...
app.get('/item/:itemid', auth.checkPerm, routes.item.get);

You can stack middleware before your final route handler like the above line has. It has to have same function signature and call next();