Question 1

Explain the difference between require() and import in Node.js.

Accepted Answer

`require()` is the synchronous, runtime loading mechanism used by the CommonJS module system, while `import` is the static, compile-time loading mechanism used by ECMAScript Modules (ESM). Because `require()` is dynamic, it can be called conditionally inside `if` statements, whereas standard `import` statements must reside at the top-level of the file. To use `import` in Node.js, you must either use the `.mjs` extension or set `"type": "module"` in `package.json`.

Question 2

Explain how modules work in Node.js.

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes very basic JavaScript familiarity, no prior module-system knowledge required. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The caching behavior below was **actually verified** on Node v24.19.0 — a real file's body executed once across two `require()` calls, not assumed from documentation. ## 1. Why This Even Matters —

Question 3

How do you replicate __dirname in ES Modules using import.meta.url?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js ESM-migration interviews — assumes basic familiarity with CommonJS's `__dirname`. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the crash and the fix below were **actually run** in a real ESM file — a genuine `ReferenceError` with its exact message, and a genuinely correct reconstructed path, not illustrative output. ## 1. Why This Even

Question 4

What is the purpose of `__dirname` and `__filename` in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes very basic file-path familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The values below were printed from a **real file on disk**, deliberately not from `node -e`, which was checked first and produces misleading placeholder values instead. ## 1. Why This Even Matters — A Story First A person gives directions

Question 5

What is the difference between "type": "module", .mjs, and .cjs?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js module-system interviews — assumes basic familiarity with CommonJS `require()` and ESM `import`. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every behavior below was **actually run** on Node v24.19.0 in a real project directory — genuine console output and a genuine real error message, not descriptions of intended behavior. ## 1. Why This

Question 6

What is top-level await and what are its caveats in Node.js ESM?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js ESM and async-architecture interviews — assumes familiarity with the module-type question's real require(ESM) boundary. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both timing claims below were **actually measured** with real `Date.now()` deltas around real `setTimeout`-based delays — genuine milliseconds, not illustrative numbers. ## 1.

Question 7

Describe the Node.js module system. What are CommonJS and ES Modules?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes basic `import`/`export` syntax familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every interop claim below was **actually executed** on Node v24.19.0, including a genuinely surprising interop detail found while testing rather than assumed. ## 1. Why This Even Matters — A Story First Two countries share a bo

Question 8

How do you handle circular dependencies in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic `require()`/module-caching familiarity (see the dedicated modules question). **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The circular-require scenario below was **actually run** on Node v24.19.0 — real console output, including a real runtime warning Node itself printed, not a description of expected behavior. ##

Question 9

How does CommonJS `require()` an ES Module in modern Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for senior Node.js interviews — assumes CommonJS vs ESM basics. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both outcomes below — the success and the failure — were **executed against Node v24.19.0**, and the exact error text is pasted from that run. ## 1. Why This Even Matters — A Story First Two departments in a company speak different languages and

Question 10

What is the package.json "exports" field and conditional exports?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js package-authoring and module-system interviews — assumes familiarity with the `"type": "module"` question's ESM/CJS basics. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the conditional resolution and the blocked path below were **actually run** — a genuine `require()` resolving one real file, a genuine `import()` resolving a different

NODE.JSDECODED.

Easy