Implement Promisify in JavaScript | Convert Callback to Promise | JS Interview Question Explained

Published: 21 February 2026
on channel: LetsCode
15
1

In this video, we implement Promisify in JavaScript from scratch and understand how to convert a callback-based function into a Promise-based function.

Promisify is a very common JavaScript interview question and an important concept for mastering async programming.

If you're preparing for frontend or JavaScript interviews, this is a must-know topic.

🚀 What You’ll Learn

What problem Promisify solves

Callback vs Promise difference

Step-by-step implementation of a promisify function

If you’re targeting:

Frontend Developer roles

JavaScript Developer interviews

React interviews

Senior frontend positions

This topic is extremely important.

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#javascript #interviewquestions #promise #frontenddeveloper #programming


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