req.headers for HTTP headers in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is req.headers in Express?

req.headers is an object in Express that contains all the HTTP headers sent by the client in a request.

beginner

How do you access the 'Content-Type' header from req.headers?

You can access it using req.headers['content-type']. Header names are case-insensitive but usually lowercase in req.headers.

beginner

True or False: req.headers keys are case-sensitive.

False. HTTP headers are case-insensitive, and Express normalizes them to lowercase in req.headers.

intermediate

Why might you check req.headers['authorization'] in an Express app?

To get the authorization token or credentials sent by the client, often used for checking if the user is allowed to access a resource.

beginner

What happens if you try to access a header that was not sent in the request?

You get undefined because that header does not exist in req.headers.

What type of data structure is req.headers in Express?

A An object with header names as keys

B An array of header strings

C A string containing all headers

D A function to get headers

req.headers is an object where each key is a header name and the value is the header's value.

How are header names stored in req.headers?

A Uppercase

B Mixed case as sent by client

C Lowercase

D Random case

Express converts all header names to lowercase in req.headers for consistency.

If a client sends no 'Authorization' header, what is req.headers['authorization']?

A An empty string

B undefined

C Throws an error

D null

Accessing a missing header returns undefined.

Which header would you check to find the type of data sent in the request body?

A content-length

B accept

C authorization

D content-type

The content-type header tells the server the format of the request body.

Why is it important to check req.headers in an Express app?

A To read client data like tokens or content type

B To send headers to the client

C To modify the request URL

D To close the connection

req.headers lets you read information sent by the client, such as tokens or data format.

Explain what req.headers is and how you use it in an Express app.

Think about how the server reads info sent by the browser or client.

Describe a real-life example where checking req.headers is useful in a web app.

Imagine you want to know who is sending the request or what kind of data they sent.