Level 0 exam — Node.js

Exam — fresh questions

12 questions to validate getting started: nature of Node and event loop, LTS workstation + VS Code, REPL and first scripts with Salim.
Answer everything, then click Check: your score and explanations will appear.

0.1 · Recall

1. What is Node.js?

A complete web browser An environment that runs JavaScript outside the browser via V8 A package manager by itself A code editor like VS Code

Node = server-side JS and tooling, via the V8 engine plus system access.

0.1 · Application

2. Salim runs: console.log("Start") ; setTimeout(() => console.log("Response"), 100) ; console.log("End"). What order?

All three at the same time End, Response, Start Response, Start, End Start, End, then Response

The program does not wait: End arrives before the callback response.

0.1 · Application

3. Salim must pick a tech for an API that waits a lot on a database. Why does Node fit?

Because it blocks on each wait Because its non-blocking model frees the thread during I/O waits Because it creates one thread per pixel Because it refuses multiple connections

Non-blocking + event loop: ideal for I/O with lots of waiting.

0.1 · Arbitration

4. Salim is offered massive 100% compute video encoding on the single Node thread. What verdict?

Accept if you add console.log Accept in REPL mode only Perfect, this is Node's home turf Refuse as is: CPU-intensive, it would block the loop — offload elsewhere

Node excels at I/O; heavy computation hogs the thread and blocks everything.

0.2 · Recall

5. Which Node version should you pick to learn and ship?

The current LTS: stable, compatible and maintained for a long time An end-of-life version with no fixes None, Node is not versioned The newest least stable Current

Current LTS = stability, npm compatibility and long support.

0.2 · Application

6. Salim just installed Node in Algiers. What action checks everything is in place?

Display both versions (Node and npm) in the terminal and run a console.log Delete the terminal Code without checking anything Open a random web page

Two numbers displayed + a running script = Node in the PATH.

0.2 · Application

7. Two of Salim's projects require two different Node versions. What does he need?

Give up the terminal A new laptop per project A version manager like nvm to switch between versions Current each time

nvm installs several versions side by side; the installer alone handles only one.

0.2 · Arbitration

8. A colleague wants to learn on an unstable Current and avoid the terminal. What to decide?

Follow along: newer means better, no terminal Require the current LTS + learning the VS Code integrated terminal Take an end-of-life version Code in the REPL only

LTS for stability, unavoidable terminal softened by VS Code.

0.3 · Recall

9. REPL or .js file: what is each for?

Both save the same Neither can run JS REPL to develop durably, file for nothing REPL to experiment fast as throwaway; .js file to develop durably

REPL = ephemeral draft; node app.js = saved and versionable work.

0.3 · Application

10. Salim runs node app.js Salim with the template (prenom = argv[2] || "Salim"). What does the first line display?

A complete HTML page Nothing, the file does not run Hello, Node ! Bienvenue Salim. window is defined

The Salim argument is read from process.argv and inserted into the message.

0.3 · Application

11. In his script, Salim types window.document. What happens under Node?

Nothing special, it is identical to the browser The page displays Error: window and document do not exist in Node, no DOM The file converts to an API

No page in Node: use process, __dirname and system access.

0.3 · Arbitration

12. Salim wrote 200 unsaved lines in the REPL and wants to keep going like this. What verdict?

Switch to a .js file: saved, re-readable, versionable; keep the REPL for tries Rewrite everything on each run Look for window to save Continue: the REPL is made for big lasting programs

Beyond two lines, the file is required; the REPL stays the draft.

What's next?

Score ≥ 80%: move to Level 1 — Modern JavaScript and async (callbacks, Promises, async/await, modules, npm).
Score between 50% and 80%: revisit the failed section(s) (0.1 model, 0.2 LTS workstation, 0.3 REPL and scripts), reread the explanations above, then retake the test.
Score < 50%: reread all of level 0 applying each 48h challenge (non-blocking script, checked workstation, app.js with argument) before retrying.
And next? Keep your Salim app.js: level 1 reuses it for modules and first npm dependencies.