Web Development — Test 4

Correct Answer: C. Number.isNaN(x)
Explanation: NaN is never equal to itself, so comparing with == or === always fails.

Correct Answer: B. It makes a shallow copy: a new array, but the same object references inside it
Explanation: Use structuredClone(a) for a deep copy.

Correct Answer: C. Attaching one listener to a parent element and handling events from its children through bubbling, using event.target
Explanation: Delegation also works for child elements added after the listener was attached.

Correct Answer: D. A new array with the callback's result for each element; the original array is unchanged
Explanation: forEach returns undefined, and reduce returns a single accumulated value.

Correct Answer: A. It is a JavaScript runtime built on V8 that uses an event-driven, non-blocking I/O model, mainly for server-side code
Explanation: Express is a popular web framework for Node.js.

Correct Answer: C. The element acts as relatively positioned until a scroll threshold is reached, then sticks like a fixed element within its container
Explanation: It needs a threshold such as top: 0, and an ancestor with overflow: hidden can stop it from working.

Correct Answer: A. It lets the browser choose an appropriately sized image for the screen's resolution and size
Explanation: It is often combined with sizes, or with the <picture> element for art direction.

Correct Answer: D. VPS (Virtual Private Server)
Explanation: Shared hosting is the cheapest but shares resources between sites. A dedicated server is a whole physical machine.

Correct Answer: B. An A record
Explanation: Use an AAAA record for IPv6 and a CNAME record to alias one hostname to another.

Correct Answer: A. Cookies are sent to the server with every matching HTTP request; localStorage stays in the browser and is never sent automatically
Explanation: Large cookies add overhead to every request, which is why bulky data belongs in localStorage. ALSO KNOW (related points): • In MVC architecture, what does the Controller do? → It handles input, works with the Model, and selects the View to render • What does a WebSocket provide? → A persistent, full-duplex connection between the browser and the server, for real-time data • What two things does a Progressive Web App (PWA) need to be installable? → A web app manifest and a service worker, served over HTTPS