JavaScript Quiz — 7 Free Questions

Question 1

What is the purpose of the browser's "Intersection Observer" API?

Question 2

What is "callback hell" (or the "pyramid of doom"), as a common criticism of deeply nested JavaScript callbacks?

Question 3

What is the difference between a JavaScript "macrotask" (such as a setTimeout callback) and a "microtask" (such as a Promise callback)?

Question 4

What is the purpose of JavaScript's "Array.prototype.splice()" method?

Question 5

What is the purpose of "code splitting", as commonly performed by a JavaScript bundler?

Question 6

What is the purpose of JavaScript's "event.preventDefault()" method?

Question 7

What is the purpose of the JavaScript "Set" object?

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About JavaScript

JavaScript has one of the most famous origin stories in programming: Brendan Eich wrote the first version in just ten days in 1995 while working at Netscape, under intense pressure to ship something that could make web pages interactive before a competing technology could get there first. The language actually went through two name changes in its earliest days, briefly called Mocha and then LiveScript, before Netscape settled on "JavaScript" largely as a marketing move to ride on the popularity of Sun's unrelated Java language.

Despite that rushed, somewhat opportunistic start, JavaScript went on to become the only programming language that runs natively in every web browser on Earth, a position of total dominance no other language has ever managed to challenge. It was later standardized under the name ECMAScript, maintained by a technical committee called TC39, which is why you'll sometimes see modern JavaScript features referred to by their ECMAScript version number instead.

For its first decade or so, JavaScript stayed mostly confined to the browser, handling small interactive touches on otherwise mostly static pages. That changed permanently with the arrival of Node.js in 2009, which let developers run JavaScript on the server too, meaning the same language could suddenly power an entire application, front end and back end, without switching languages halfway through.

Node.js also brought npm along with it, a package registry for sharing reusable JavaScript code, which has since grown into the largest software package registry in the world by a wide margin, hosting well over a million packages covering nearly anything a developer might need.

JavaScript's ecosystem has also become famous, and occasionally mocked, for the sheer number of frameworks and tools that come and go, a phenomenon developers often jokingly call "framework fatigue." Partly in response to some of JavaScript's looser, more error-prone typing habits, TypeScript emerged as a popular superset of the language that adds optional static typing, and it has since become close to a default choice for large-scale JavaScript projects.

A major turning point for JavaScript's real-world performance came with Google's V8 engine, originally built to power Chrome, which dramatically sped up JavaScript execution and directly enabled Node.js to exist as a genuinely fast server-side platform in the first place. That combination of running everywhere a browser exists and being fast enough to run servers too is a big part of why JavaScript is consistently ranked as the most widely used programming language in the world today.

More recently, WebAssembly has opened up an entirely new set of possibilities for the browser, letting code written in languages like C++, Rust, or Go run inside web pages at near-native speed alongside JavaScript rather than instead of it. Rather than replacing JavaScript, WebAssembly has mostly ended up complementing it, handling performance-critical tasks like video editing or games while JavaScript continues to manage the overall page and user interface.

JavaScript's dominance also means it's often the very first programming language many people encounter, whether through a coding bootcamp, a university course, or simply poking at a browser's developer console out of curiosity, giving it an outsized role in how an entire generation of developers first learned to think about code.