Question 1

What are modules in JavaScript?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The module-caching claim below was actually run and confirmed inside a real CommonJS script. ## 1. Why This Even Matters — A Story First A shared office supply closet, restocked once at the start of the day, is used identically by every single department that visits it

Question 2

What is an IIFE?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The scoping and immediate-execution claims below were actually run in Node. ## 1. Why This Even Matters — A Story First Think of a magician who steps behind a curtain, does some private setup work, and immediately steps back out — the audience never sees, and can never

Question 3

What is the difference between ES modules and CommonJS?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript/Node.js fundamentals interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The caching and environment claims below were actually run in Node, directly inside a real CommonJS script. ## 1. Why This Even Matters — A Story First CommonJS's `require()` is like asking a librarian in person for a book by a title you might decide on the s

Question 4

What does 'use strict' do?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every sloppy-vs-strict contrast below was actually run in Node — not recited from documentation. ## 1. Why This Even Matters — A Story First Sloppy mode is like a lenient proofreader who quietly fixes your typos without telling you — convenient in the moment, but it

Question 5

How does top-level await change how an ES module and its importers load, and what are the risks of using it carelessly?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript module-system interviews. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every timestamp and error below is **real, captured output** — a live browser run, a real Node ESM run with actual millisecond timestamps, and a genuine crash reproduction — not illustrative sample output. ## 1. Why This Even Matters — A Story First A relay race where

JAVASCRIPTDECODED.

Medium

What are modules in JavaScript?

What is an IIFE?

What is the difference between ES modules and CommonJS?

What does 'use strict' do?

Hard

How does top-level await change how an ES module and its importers load, and what are the risks of using it carelessly?