promisify

Promisify is a common pattern in asynchronous programming, particularly in JavaScript, used to convert callback-based asynchronous functions into Promise-based functions. Callback-based functions typically accept a final argument that is a function itself, often referred to as a callback. This callback is executed when the asynchronous operation completes, and it usually receives an error argument as its first parameter and the result as subsequent parameters.

The promisify pattern aims to simplify working with such functions by wrapping them in a Promise. When the promisified function is called, it returns a new Promise. Inside the Promise constructor, the original callback-based function is invoked. The callback provided to the original function is then modified to either resolve the Promise with the result if the operation was successful or reject the Promise with the error if an error occurred.

This transformation is highly beneficial because it allows developers to chain asynchronous operations using .then() and .catch() methods, or to use async/await syntax, which leads to more readable and manageable asynchronous code. Many Node.js modules provide utility functions, such as `util.promisify` in Node.js's built-in `util` module, to easily convert callback-style functions into their Promise-returning equivalents. The core idea is to abstract away the complexities of callback management and error handling into a more modern and structured Promise-based interface.