Route parameters in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are route parameters in Express?

Route parameters are parts of the URL that act as placeholders for values. They let you capture values from the URL and use them in your code.

beginner

How do you define a route parameter in an Express route?

You define a route parameter by adding a colon (:) before a name in the route path, like '/user/:id'. This means 'id' is a parameter you can access.

beginner

How do you access route parameters inside an Express route handler?

You access route parameters using 'req.params'. For example, if your route is '/user/:id', you get the id with 'req.params.id'.

intermediate

What happens if you define multiple route parameters in Express?

You can define multiple parameters like '/user/:userId/book/:bookId'. Each parameter is available in 'req.params' by its name, e.g., 'req.params.userId' and 'req.params.bookId'.

intermediate

Can route parameters be optional in Express? How?

Yes, by adding a question mark (?) after the parameter name, like '/user/:id?'. This means the parameter is optional and the route matches with or without it.

How do you define a route parameter named 'postId' in Express?

A /post/?postId

B /post/postId

C /post/:postId

D /post/*postId

Route parameters are defined with a colon before the name, like '/post/:postId'.

Where do you find the value of a route parameter inside an Express route handler?

A req.body

B req.params

C req.query

D req.headers

Route parameters are stored in 'req.params' as key-value pairs.

What does the route '/user/:id?' mean in Express?

A The 'id' parameter is required

B The route matches only if 'id' is a string

C The route matches only if 'id' is a number

D The 'id' parameter is optional

Adding '?' after a parameter name makes it optional.

If you have a route '/product/:category/:id', how do you access the 'category' parameter?

A req.params.category

B req.query.category

C req.body.category

D req.headers.category

Route parameters are accessed via 'req.params' by their names.

Which of these is NOT a valid route parameter definition in Express?

A /item/itemId

B /item/:itemId/details

C /item/:itemId

D /item/:itemId?

Without a colon, 'itemId' is treated as a fixed path segment, not a parameter.

Explain how to create and use route parameters in Express routes.

Think about how URLs can carry data like user IDs.

Describe how to make a route parameter optional and why you might want to do that.

Optional means the URL can have that part or skip it.