Built-in middleware (json, urlencoded, static) in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the built-in middleware express.json() do in an Express app?

express.json() parses incoming requests with JSON payloads. It makes the JSON data available on req.body.

beginner

How does express.urlencoded() middleware help in handling form data?

express.urlencoded() parses incoming requests with URL-encoded payloads, like form submissions. It makes form data accessible on req.body.

beginner

What is the purpose of express.static() middleware?

express.static() serves static files like images, CSS, and JavaScript from a folder. It helps deliver these files directly to the browser.

beginner

How do you use express.static() to serve files from a folder named public?

You add app.use(express.static('public')) in your Express app. This makes files in public accessible via URLs.

intermediate

Why is it important to use express.json() and express.urlencoded() middleware before your route handlers?

Because they parse the request body first, so your route handlers can easily access the data on req.body. Without them, req.body would be undefined.

Which middleware parses JSON data in an Express app?

A express.json()

B express.urlencoded()

C express.static()

D bodyParser.text()

express.json() is used to parse JSON payloads in requests.

What type of data does express.urlencoded() parse?

A URL-encoded form data

B Cookies

C Static files

D JSON data

express.urlencoded() parses URL-encoded form data, like from HTML forms.

How do you serve static files from a folder named assets?

A app.get('/assets')

B app.use(express.static('assets'))

C app.use(express.json('assets'))

D app.use(express.urlencoded('assets'))

express.static('assets') serves static files from the assets folder.

What will happen if you don't use express.json() before accessing req.body for JSON data?

A Static files will not load

B <code>req.body</code> will contain parsed JSON

C Server will crash

D <code>req.body</code> will be undefined

Without express.json(), Express does not parse JSON, so req.body is undefined.

Which middleware should you use to handle form submissions with method POST?

A express.json()

B express.static()

C express.urlencoded()

D express.raw()

express.urlencoded() parses URL-encoded form data sent via POST.

Explain how express.json(), express.urlencoded(), and express.static() middleware work and when to use each.

Think about the type of data each middleware handles and how it helps your app.

Describe the steps to serve static files and handle JSON and form data in an Express app using built-in middleware.

Focus on the order and purpose of each middleware.