Node.js matching the url pattern

Question

I need an equivalent of following express.js code in simple node.js that I can use in middleware. I need to place some checks depending on the url and want to do it in a custom middleware.

app.get "/api/users/:username", (req,res) ->
  req.params.username

I have the following code so far,

app.use (req,res,next)->
  if url.parse(req.url,true).pathname is '/api/users/:username' #this wont be true as in the link there will be a actual username not ":username" 
    #my custom check that I want to apply

Answer 1

A trick would be to use this:

app.all '/api/users/:username', (req, res, next) ->
  // your custom code here
  next();

// followed by any other routes with the same patterns
app.get '/api/users/:username', (req,res) ->
  ...

If you only want to match GET requests, use app.get instead of app.all.

Or, if you only want to use the middleware on certain specific routes, you can use this (in JS this time):

var mySpecialMiddleware = function(req, res, next) {
  // your check
  next();
};

app.get('/api/users/:username', mySpecialMiddleware, function(req, res) {
  ...
});

EDIT another solution:

var mySpecialRoute = new express.Route('', '/api/users/:username');

app.use(function(req, res, next) {
  if (mySpecialRoute.match(req.path)) {
    // request matches your special route pattern
  }
  next();
});

But I don't see how this beats using app.all() as 'middleware'.

Answer 2

You can use node-js url-pattern module.

Make pattern:

var pattern = new UrlPattern('/stack/post(/:postId)');

Match pattern against url path:

pattern.match('/stack/post/22'); //{postId:'22'}
pattern.match('/stack/post/abc'); //{postId:'abc'}
pattern.match('/stack/post'); //{}
pattern.match('/stack/stack'); //null

For more information, see: https://www.npmjs.com/package/url-pattern

Answer 3

Just use the request and response objects as you would in a route handler for middleware, except call next() if you actually want the request to continue in the middleware stack.

app.use(function(req, res, next) {
  if (req.path === '/path') {
    // pass the request to routes
    return next();
  }

  // you can redirect the request
  res.redirect('/other/page');

  // or change the route handler
  req.url = '/new/path';
  req.originalUrl // this stays the same even if URL is changed
});