app.METHOD(PATH, HANDLER) app is an instance of express. METHOD is an HTTP request method, in lowercase. PATH is a path on the server. HANDLER is the function executed when the route is matched.

What is routing?

Difficulty: 5/10

basic routing, router middleware, dynamic routes

Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, and so on).

Route definition takes the following structure:

Where:

1
app is an instance of express.
2
METHOD is an HTTP request method, in lowercase.
3
PATH is a path on the server.
4
HANDLER is the function executed when the route is matched.

Scenario Questions

0-2 years experience

1You need to add an endpoint that returns a list of products at GET /products. Walk me through how you would set up the route in an Express app.
2If a request comes to /users/123 and you have defined app.get('/users/:id'), what value will req.params.id contain and how would you use it?
3What happens if you define two routes with the same path but different HTTP methods, like app.get('/login') and app.post('/login')? How does Express decide which handler runs?

Follow-up Questions

Can you show a quick code snippet for that?
What edge cases might break this routing setup?
How would you verify it works in production?