Mounting routers with app.use in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does app.use() do in Express when mounting routers?

app.use() attaches a router or middleware to a specific path in your Express app. It tells the app to use that router for all requests starting with that path.

beginner

How do you mount a router on the path /users using app.use()?

First, create a router with express.Router(). Then use app.use('/users', userRouter). This means all routes inside userRouter will start with /users.

beginner

Why is mounting routers useful in Express?

It helps organize your code by grouping related routes together. For example, all user-related routes can be in one router, making your app easier to read and maintain.

intermediate

What happens if you mount a router without a path in app.use()?

If you use app.use(router) without a path, the router handles requests starting from the root /. All routes inside the router are used as is.

beginner

Can you mount multiple routers on different paths using app.use()?

Yes! You can mount as many routers as you want on different paths. For example, app.use('/users', userRouter) and app.use('/products', productRouter) keep routes separate and organized.

What does app.use('/api', apiRouter) do?

A Removes the <code>/api</code> prefix from routes inside <code>apiRouter</code>

B Runs <code>apiRouter</code> only for the root path <code>/</code>

C Mounts <code>apiRouter</code> so all its routes start with <code>/api</code>

D Creates a new Express app

This mounts apiRouter so all its routes are prefixed with /api. For example, /api/users.

Which Express method is used to create a router to mount with app.use()?

A express.createRouter()

B app.createRouter()

C app.router()

D express.Router()

express.Router() creates a new router instance.

If you mount a router with app.use(router) without a path, what is the base path for its routes?

A /

B /router

C /api

D No base path

The base path is /, so routes inside the router are used as defined.

Why might you want to use multiple routers in an Express app?

A To slow down the app

B To organize routes by feature or section

C To avoid using middleware

D To prevent routing

Multiple routers help organize routes by feature, making code easier to manage.

What is the correct way to mount a router for admin routes at /admin?

A app.use('/admin', adminRouter)

B app.use(adminRouter, '/admin')

C app.mount('/admin', adminRouter)

D app.router('/admin', adminRouter)

The syntax is app.use('/admin', adminRouter) to mount the router at /admin.

Explain how mounting routers with app.use() helps organize an Express application.

Think about how you separate different parts of a website into folders.

Describe the difference between mounting a router with and without a path in app.use().

Consider what happens to the URL when you add a prefix.