DevAcademy

1. What does emitter.once() do differently from emitter.on()?

It runs the listener every timeIt runs the listener only for the first occurrence of the event, then removes itIt removes all listeners immediatelyIt only works with the "error" event

2. Do EventEmitter listeners run synchronously or asynchronously when emit() is called?

Asynchronously, alwaysSynchronously, in registration orderRandomly orderedOnly one listener runs per emit

3. What happens if an EventEmitter emits an "error" event with no listener attached?

Nothing happensIt throws and can crash the processIt is silently loggedIt is automatically retried

4. What advantage do streams have over reading an entire file into memory at once?

They are always faster for small filesThey process data in chunks, keeping memory usage low regardless of file sizeThey automatically compress dataThey eliminate the need for error handling

5. What does .pipe() do?

Deletes a streamConnects a readable stream's output directly into a writable stream's inputConverts a stream to a stringPauses a stream forever

6. What is backpressure in the context of streams?

An error state that always crashes the processAn automatic mechanism that pauses a fast readable stream until a slower writable stream catches upA type of compressionA way to skip chunks of data

7. What does a Buffer represent?

A JavaScript objectA fixed-length chunk of raw binary dataA type of PromiseA CSS style

8. Does Buffer.length measure bytes or characters?

CharactersBytesAlways the same thingNeither

9. What type of data do readable streams emit by default?

StringsBuffer chunksArraysJSON objects

10. What is process.nextTick() relative to resolved Promise callbacks?

Lower priorityHigher priority — it runs before promise microtasksIdentical priorityIt does not exist

11. In the ordering example, why does synchronous code ("1" and "5") run before everything else?

It is randomSynchronous code always runs to completion before any queued async callbacksetTimeout always runs firstIt depends on file size

12. What can happen if process.nextTick() is called recursively without bound?

Nothing, it is always safeIt can starve I/O, since nextTick callbacks run before the event loop proceedsIt automatically times out after 1 secondIt only affects setTimeout

13. What does setTimeout(fn, 0) actually guarantee?

fn runs immediately, synchronouslyfn is scheduled to run on a later event loop iteration, not immediatelyfn never runsfn runs before any synchronous code

14. What is a common cause of memory leaks involving timers?

Using setTimeout at allA setInterval left running with no reference kept to clear it laterUsing async/awaitTimers cannot cause memory leaks

15. How can setTimeout be used to build an awaitable delay?

It cannot be combined with PromisesWrap it in a Promise that resolves inside the setTimeout callbackUse await setTimeout() directlyOnly setInterval supports this

16. Do you need to import process in Node.js scripts?

Yes, alwaysNo, it is a global object available automaticallyOnly in ES ModulesOnly for CLI tools

17. What does process.argv contain?

Environment variablesCommand-line arguments passed to the scriptThe current file path onlyHTTP request headers

18. Why listen for the SIGTERM signal in a server?

It has no practical useTo shut down gracefully, finishing in-flight work before exitingIt is required by npmIt only matters for CLI scripts

19. Are frameworks like Express built on top of the core http module?

No, they replace it entirelyYes, they are built on top of itOnly in older versionsThey are unrelated

20. What does the raw http module lack that frameworks typically add?

The ability to receive requests at allBuilt-in routing, body parsing, and middlewareAny way to send a responseSupport for JSON

21. What method sends the response headers and status code?

res.send()res.writeHead(status, headers)res.headers()req.respond()

22. How does a raw http server determine which route to serve?

Automatically, based on file namesManually, by inspecting req.method and req.url with conditional logicIt cannot route requests without a frameworkUsing a built-in router object

23. How does a raw http server body arrive?

As a ready-made parsed JavaScript objectAs a stream of data chunks that must be collected manuallyIt cannot receive a bodyAs a file on disk

24. What HTTP status code conventionally indicates a resource was successfully created?

200201204400

25. What is Express built on top of?

MongoDBThe core http moduleReactTypeScript

26. What does res.json({ users: [] }) do?

Sends a plain text responseSends a JSON response with the correct Content-Type header set automaticallyOnly logs to the consoleRedirects the request

27. What does "unopinionated" mean about Express?

It has no features at allIt doesn't enforce a particular project structure or architectureIt cannot be customizedIt only supports one database

28. How do you access a value from a dynamic route parameter like /users/:id?

req.query.idreq.params.idreq.body.idreq.id

29. What does express.Router() provide?

A way to connect to a databaseA way to define a group of routes in a separate, mountable moduleA built-in ORMA testing framework

30. Which method registers a handler for HTTP DELETE requests?

app.remove()app.delete()app.destroy()app.del()

Node.js Intermediate Practice

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