expressjs re-routing originally published: Jan 2013

One of the most common questions I get asked when I talk about express is how I manage my routes. While I generally point out things like app.param() and other middleware tricks, I am left just saying that I don't have a great solution. Well, I am happy to say that as of express 3.0.6 I have a better answer; use the router!

Routes, why do I care?

Maybe you don't like routers, but they do serve a purpose. If you are writing a web app or even a headless api, you can benefit from the simple separation and organization a nice router will provide. Just think of it as a URL if statement on steroids!

The typical express application looks something like this:

var app = express (); /// top level routes app . get ( '/' , function ( req , res , next ) { ... } ); /// blog post routes app . get ( '/post/:post_id' , function ( req , res , next ) { ... }); app . post ( '/post/:post_id/comment' , function ( req , res , next ) { ... }); app . del ( '/post/:post_id/comment' , function ( req , res , next ) { ... }); /// etc

As the number of routes you want your app to handle grows, you might find that this single file approach gets out of control (justifiably so) and move to a multi-file approach where you export handler functions.

var post = require ( './routes/post' ); app . get ( '/post/:post_id' , post . get ); app . post ( '/post/:post_id/comment' , post . addComment ); app . del ( '/post/:post_id/comment' , post . removeComment );

The problem is that your routes/post file is now void of the actual route information. This can make it a bit more challenging to see what is going on and debug.

Router to the rescue!

Instead of exporting individual functions from your routes files. You can now use the express router without creating a whole new express app.

Imagine we have the following routes.js file

var express = require ( 'express' ); var router = new express . Router (); // we can use all of the HTTP verbs on the router router . get ( '/bar' , function ( req , res , next ) { ... }); router . post ( '/baz' , function ( req , res , next ) { ... }); // at the end we export this router as a single unit module . exports = router ;

And in app.js

var app = express (); // this is for the routes in this file app . use ( app . router ); // this creates /foo/bar and /foo/baz // /foo could be any prefix app . use ( '/foo' , require ( './routes' ). middleware ); // our typical app routes can still go here app . get ( '/' , function ( req , res , next ) { ... });

What we have done is left the relevant path information in the routes.js file and "mounted" those routes under the /foo url. Now we have basic routes and handlers defined separately from where the parent application may be mounting them.

Note: You could app.use(require('./routes').middleware); if you wanted to host the routes from the site root.

Complete app example

I have created a gist which you can clone or review below as a more complete example.

app.js

Our main app.js (server.js, index.js, whatever.js) file does not change much. The only major difference is that instead of using app.get for our /user and /post routes in the file, we use app.use and inject them under their respective parent urls.

routes/user.js

We now put all of the routes we want to contain as one unit in this file. Notice that this file does not know that it will be served under /user . It could be served from any route by a parent file. Using this approach you could reuse sets of routes in multiple places (not suggesting this is what you want :)

routes/post.js

Like the app, the router has a .param() function which allows you to consolidate parameter handling. In this example, we see that since all of these routes will need a post, we use the :post_id parameter from the url to make sure a post is loaded before any route is run.