Use specific middleware in Express for all paths except a specific one

Problem

I am using the Express framework in node.js with some middleware functions:

var app = express.createServer(options);
app.use(User.checkUser);

I can use the .use function with an additional parameter to use this middleware only on specific paths:

app.use('/userdata', User.checkUser);

Is it possible to use the path variable so that the middleware is used for all paths except a specific one, i.e. the root path?

I am thinking about something like this:

app.use('!/', User.checkUser);

So User.checkUser is always called except for the root path.

Problem courtesy of: Thomas

Solution

I would add checkUser middleware to all my paths, except homepage.

app.get('/', routes.index);
app.get('/account', checkUser, routes.account);

or

app.all('*', checkUser);

function checkUser(req, res, next) {
  if ( req.path == '/') return next();

  //authenticate user
  next();
}

You could extend this with underscore to search for the req.path in an array of non-authenticated paths:

function checkUser(req, res, next) {
  var _ = require('underscore')
      , nonSecurePaths = ['/', '/about', '/contact'];

  if ( _.contains(nonSecurePaths, req.path) ) return next();

  //authenticate user
  next();
}
Solution courtesy of: chovy

Discussion

Instead of directly registering User.checkUser as middleware, register a new helper function, say checkUserFilter, that gets called on every URL, but passed execution to userFiled` only on given URLs. Example:

var checkUserFilter = function(req, res, next) {
    if(req._parsedUrl.pathname === '/') {
        next();
    } else {
        User.checkUser(req, res, next);
    }
}

app.use(checkUserFilter);

In theory, you could provide regexp paths to app.use. For instance something like:

app.use(/^\/.+$/, checkUser);

Tried it on express 3.0.0rc5, but it doesn't work.

Maybe we could open a new ticket and suggest this as a feature?

Discussion courtesy of: jsalonen

You can set the middleware one each route also.

// create application/x-www-form-urlencoded parser
var urlencodedParser = bodyParser.urlencoded({ extended: false })

// POST /login gets urlencoded bodies
app.post('/login', urlencodedParser, function (req, res) {
  if (!req.body) return res.sendStatus(400)
  res.send('welcome, ' + req.body.username)
})
Discussion courtesy of: Jonatan Lundqvist Medén

Use

app.use(/^(\/.+|(?!\/).*)$/, function(req, resp, next){...

This pass any url apart from /. Unless, it works for me.

In general

/^(\/path.+|(?!\/path).*)$/

(see How to negate specific word in regex?)

Hope this helps

Discussion courtesy of: user1872904

This recipe can be found in it's original form on Stack Over Flow.