Question 1

What is the purpose of the util.promisify function in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes basic Promise and callback familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the success and rejection paths below were **actually executed** on Node v24.19.0, not assumed from the function's name. ## 1. Why This Even Matters — A Story First An old appliance with a two-prong plug still works perfectly —

Question 2

What are Promises in Node.js and how do they improve async code?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/JavaScript interviews — assumes basic callback familiarity, no prior Promise knowledge required. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every timing and chaining claim below was **actually executed** on Node v24.19.0. ## 1. Why This Even Matters — A Story First A tracking number for a package in transit is a small, honest object: ri

Question 3

How does `async/await` work and what are its benefits?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/JavaScript interviews — assumes basic Promise familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every claim below — including that an async function's return value really is a Promise — was **actually executed and inspected**, not assumed from how the syntax reads. ## 1. Why This Even Matters — A Story First A recipe written as "w

Question 4

What does the events.once() helper do and how does it bridge EventEmitter and async/await?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js EventEmitter and async/await interoperability interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the real event-timing match and the real error-rejection behavior below were **actually run** — genuine timestamps and a genuine caught rejection, not descriptions of documented behavior. ## 1. Why This Even Matters — A Story First

Question 5

Explain what 'callback hell' is and how to avoid it.

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/JavaScript interviews — assumes basic callback and Promise familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. All three versions of the example below were **actually executed** on Node v24.19.0 and produced identical results — pasted below, not assumed. ## 1. Why This Even Matters — A Story First Giving someone directions as "when

NODE.JSDECODED.

Easy

What is the purpose of the util.promisify function in Node.js?

Medium

What are Promises in Node.js and how do they improve async code?

How does `async/await` work and what are its benefits?

What does the events.once() helper do and how does it bridge EventEmitter and async/await?

Explain what 'callback hell' is and how to avoid it.