Setting response headers in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of setting response headers in Node.js?

Response headers provide metadata about the response, such as content type, caching rules, and security policies. They help the browser understand how to handle the response.

beginner

How do you set a single response header in Node.js using the http module?

Use the response object's setHeader method, like: res.setHeader('Content-Type', 'application/json').

intermediate

What happens if you try to set a header after the response has been sent?

Node.js will throw an error because headers must be set before sending the response body. Once headers are sent, they cannot be changed.

intermediate

How can you set multiple headers at once in Node.js?

You can use res.writeHead(statusCode, headersObject) to set status and multiple headers together, for example: res.writeHead(200, {'Content-Type': 'text/html', 'Cache-Control': 'no-cache'}).

beginner

Why is it important to set the 'Content-Type' header correctly?

It tells the browser what kind of data is being sent (like HTML, JSON, or plain text), so the browser can display or process it properly.

Which method sets a single response header in Node.js?

A res.headerSet()

B res.getHeader()

C res.sendHeader()

D res.setHeader()

The correct method to set a single header is res.setHeader().

When must response headers be set in Node.js?

A After sending the response body

B Before sending the response body

C Any time during the request

D Only after the response ends

Headers must be set before sending the response body because they are sent first.

What does the 'Content-Type' header specify?

A The type of data in the response

B The size of the response

C The server's IP address

D The client's browser version

Content-Type tells the client what kind of data is in the response.

Which method sets multiple headers and status code at once?

A res.writeHead()

B res.setHeaders()

C res.sendHeaders()

D res.setStatus()

res.writeHead() sets the status code and multiple headers together.

What happens if you set a header after calling res.end()?

A The response restarts

B The header is set successfully

C An error occurs because headers are already sent

D The header is ignored silently

Headers must be set before res.end(); otherwise, Node.js throws an error.

Explain how to set response headers in Node.js and why it is important.

Think about how the browser knows what kind of data it receives.

Describe the difference between res.setHeader() and res.writeHead() in Node.js.

One is for single headers, the other for multiple headers and status.