Request context middleware in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is request context middleware in Express?

It is a middleware that creates a shared space to store data related to a single HTTP request, allowing different parts of the app to access this data during that request.

beginner

How does request context middleware help in handling data during a request?

It keeps data like user info or request ID accessible across multiple middleware and route handlers without passing it explicitly as parameters.

beginner

Which Express object is commonly used to store request context data?

The req (request) object is often extended with custom properties to hold context data for the current request.

intermediate

Why should request context data not be stored globally in Express apps?

Because Express handles many requests at once, global data would mix information between requests, causing bugs and security issues.

beginner

Give an example of data you might store in request context middleware.

You might store a unique request ID, authenticated user details, or timing info to track how long the request takes.

What is the main purpose of request context middleware in Express?

A To store data globally for all requests

B To share data across different parts of the same request

C To handle static files

D To manage database connections

Request context middleware shares data only within the scope of a single request, not globally.

Where is request context data usually stored in Express?

A In the <code>res</code> object

B In a global variable

C In the <code>req</code> object

D In the <code>app</code> object

The req object is specific to each request and is the right place to store context data.

Why is it bad to store request data in global variables?

A It prevents bugs

B It improves performance

C It makes code easier to read

D It causes data to mix between requests

Global variables are shared across all requests, which can cause data leaks and bugs.

Which of these is NOT a typical use of request context middleware?

A Serving static images

B Tracking request duration

C Storing user authentication info

D Passing request ID

Serving static images is handled by static middleware, not request context middleware.

How can you add data to the request context in Express middleware?

A By adding properties to <code>req</code>, like <code>req.user = {...}</code>

B By modifying the <code>res</code> headers

C By changing global variables

D By editing the <code>app</code> object

Adding properties to req is the standard way to store request-specific data.

Explain what request context middleware is and why it is useful in Express apps.

Think about how to share data safely during one request.

Describe how you would implement simple request context middleware in Express.

Focus on modifying the req object inside middleware.