MEAN Express.js Middleware and Routing

Question 1

What is the correct order of arguments in an Express.js error-handling middleware function?

Accepted Answer

(err, req, res, next)

Answer

Express identifies error-handling middleware by its four-argument signature (err, req, res, next) — the error object must be the first parameter.

Question 2

Which Express.js method is used to define a route that handles all HTTP methods?

Accepted Answer

app.all()

Answer

app.all() matches all HTTP methods (GET, POST, PUT, DELETE, etc.) for the specified path, useful for authentication middleware on all routes.

Question 3

What does `express.json()` middleware do in an Express application?

Accepted Answer

Parses incoming requests with JSON payloads and populates req.body

Answer

express.json() is built-in middleware that parses the request body as JSON when Content-Type is application/json, making it available as req.body.

Question 4

How do you define a URL parameter in an Express route?

Accepted Answer

app.get('/users/:id', handler)

Answer

Express uses colon-prefixed segments like :id to define named URL parameters, which are then accessible via req.params.id.

Question 5

What is the purpose of calling `next()` in Express middleware?

Accepted Answer

Passes control to the next matching middleware or route handler

Answer

Calling next() without arguments passes control to the next middleware function in the stack; calling next(err) skips to error-handling middleware.

MEAN - Stack Development Practice Test