app.all and app.use for catch-all in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does app.all do in Express?

app.all matches all HTTP methods (GET, POST, PUT, DELETE, etc.) for a specific route path.

It is useful when you want the same handler for all request types on that path.

beginner

How does app.use differ from app.all in Express?

app.use is used to mount middleware functions that run for all HTTP methods and paths that start with the given path.

It is often used for middleware like logging, authentication, or catch-all routes.

intermediate

How can app.all be used as a catch-all route?

By using app.all('*', handler), you can catch all requests to any path and any HTTP method that were not matched earlier.

This is useful for 404 pages or default responses.

intermediate

What is the common use of app.use as a catch-all in Express?

Using app.use((req, res) => { ... }) without a path catches all requests not handled by previous routes.

This is often used to send a 404 response or handle errors.

beginner

Which method should you place last in your Express app to handle unmatched routes?

You should place either app.all('*', handler) or app.use((req, res) => { ... }) at the end of your route definitions.

This ensures all unmatched requests are caught and handled properly.

What does app.all('/path', handler) do in Express?

A Handles all HTTP methods for '/path'

B Handles only GET requests for '/path'

C Handles all paths for GET requests

D Mounts middleware for all paths

app.all matches all HTTP methods for the specified path.

Which Express method is best to use for middleware that runs on every request regardless of path?

A app.post()

B app.all()

C app.get()

D app.use()

app.use runs middleware for all HTTP methods and paths starting with the given path (or all paths if no path is given).

How do you create a catch-all route for unmatched requests using app.all?

A app.all('/', handler)

B app.all('*', handler)

C app.all('', handler)

D app.all('/catch', handler)

app.all('*', handler) matches all paths and methods not matched earlier.

What happens if you place app.use middleware before route handlers?

A It only runs after routes

B It will never run

C It runs before the routes and can modify requests

D It causes an error

app.use middleware runs in order and can process requests before route handlers.

Which is a good use case for app.use((req, res) => { res.status(404).send('Not found') })?

A Handling unmatched routes with 404

B Logging requests

C Serving static files

D Parsing JSON bodies

This middleware catches all unmatched requests and sends a 404 response.

Explain how app.all and app.use can be used to catch all unmatched routes in an Express app.

Think about how Express matches routes and middleware in order.

Describe the difference between app.all and app.use in Express and when to use each for catch-all behavior.

Focus on routes vs middleware roles.