Web Development Flashcards

What is CORS and why is it enforced by browsers?

Answer: A security mechanism that restricts cross-origin HTTP requests made from scripts

CORS (Cross-Origin Resource Sharing) is a browser security policy that blocks scripts from making requests to a different origin unless the server explicitly allows it.

In JavaScript, what is the output of: typeof null?

Answer: 'object'

typeof null returns 'object' — a well-known historical bug in JavaScript that has been kept for backward compatibility.

Which web performance metric measures the time until a page's main content is visually rendered?

Answer: Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest visible content element (image or text block) to fully render in the viewport.

What does the CSS 'box-sizing: border-box' declaration change?

Answer: Includes padding and border within the element's declared width and height

With border-box, padding and border are included inside the element's specified width/height instead of being added on top.

In version control with Git, what does 'git rebase' do compared to 'git merge'?

Answer: Rebase replays commits onto a new base, creating a linear history; merge creates a merge commit

Git rebase moves commits to a new base commit, producing a cleaner linear history, while merge preserves the branch topology with a merge commit.

Which JavaScript feature allows you to extract values from arrays and objects into distinct variables in a single statement?

Answer: Destructuring assignment

Destructuring assignment syntax lets you unpack values from arrays or properties from objects into separate variables concisely.

What is the main advantage of using a CDN (Content Delivery Network) for static assets?

Answer: Assets are served from edge servers geographically closer to users, reducing latency

CDNs cache and serve static files from distributed edge locations worldwide, minimizing the physical distance data must travel to reach users.