Request body transformation in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is request body transformation in Express?

It means changing or processing the data sent by the client in the request body before using it in your app.

beginner

Which middleware is commonly used in Express to parse JSON request bodies?

express.json() middleware parses incoming JSON request bodies and makes the data available on req.body.

intermediate

How can you modify the request body data in Express before using it?

You can write a middleware function that reads req.body, changes or adds properties, then calls next() to continue.

beginner

Why might you want to transform the request body in an Express app?

To clean data, add default values, convert formats, or validate input before your app uses it.

intermediate

Show a simple example of middleware that adds a timestamp to the request body.

function addTimestamp(req, res, next) {
  if (!req.body) req.body = {};
  req.body.timestamp = new Date().toISOString();
  next();
}

Which Express middleware parses JSON request bodies?

A express.json()

B express.urlencoded()

C express.static()

D express.raw()

express.json() parses JSON data in the request body and makes it available on req.body.

Where is the transformed request body data stored in Express?

A req.body

B req.params

C req.query

D req.headers

The request body data, after parsing and transformation, is stored in req.body.

What must you call in middleware after modifying req.body to continue processing?

A req.next()

B res.send()

C res.next()

D next()

Calling next() passes control to the next middleware or route handler.

Why transform request body data in Express?

A To change HTTP methods

B To clean or prepare data before use

C To modify response headers

D To serve static files

Transforming request body helps prepare data for safe and correct use in the app.

Which of these is NOT a typical request body transformation?

A Adding default values

B Validating input

C Changing URL paths

D Converting data formats

Changing URL paths is handled by routing, not request body transformation.

Explain how to use middleware in Express to transform the request body data.

Think about how middleware works in Express and how you can change req.body.

Describe why transforming the request body is useful in a web app.

Consider what happens if the app uses raw or incorrect data.