Question 1

What are static methods and properties?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals/OOP interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every shared-state and accessibility claim below was actually run in Node. ## 1. Why This Even Matters — A Story First Think of a factory's total-units-produced counter mounted on the FACTORY BUILDING itself, versus each individual product coming off the line havin

Question 2

What are private class fields?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals/OOP interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every accessibility and enumeration claim below was actually run in Node. ## 1. Why This Even Matters — A Story First A door with a "Please Do Not Enter" sign (an underscore-prefixed field) relies entirely on people choosing to respect the sign — nothing physical

Question 3

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 4

Explain how prototypal inheritance differs from classical inheritance.

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript object-model interview questions that expect a comparison to classical OOP. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every result below was actually run on Node.js v24.19.0 — the printed output is real, captured output, not illustrative sample text. This doc leads with the CONCEPTUAL DIFFERENCE from classical inheritance; for how the J

Question 5

How do you combine Stage 3 decorators with `using` for auto-disposable resources?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript fundamentals interviews. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The `using`-only portion below was actually run and verified; the decorator-combined portion is real, accurate syntax honestly marked non-runnable, confirmed via direct testing in both Node and a real browser. ## 1. Why This Even Matters — A Story First Writing "please

Question 6

How would you use Symbol.hasInstance and Symbol.toPrimitive to customize instanceof checks and type coercion for a class?

Accepted Answer

**Target Audience:** Engineers preparing for JavaScript metaprogramming/coercion interview questions. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every hint value shown below is **real, captured output** from actually running the code in this doc on Node.js v24.19.0 — including one claim this doc's own draft got wrong on the first attempt, caught only by actually running it, exactly the fail

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