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

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 5

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. ##

NODE.JSDECODED.

Easy

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

Explain how modules work in Node.js.

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

Medium

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

Hard

How do you handle circular dependencies in Node.js?