requireutilpromisify

requireutilpromisify is a built-in Node.js module that provides a utility function for promisifying callback-based functions. In essence, it allows you to convert functions that traditionally use callbacks to signal completion into functions that return Promises. This makes it easier to work with asynchronous operations in a more modern and readable style, especially when using async/await syntax.

The core of util.promisify is its ability to wrap a Node.js-style callback function (a function that expects a callback as its last argument, where the callback typically receives an error as the first argument and a result as the second) and return a new function that returns a Promise. When the original callback-based function is invoked, util.promisify intercepts the result or error from the callback and resolves or rejects the returned Promise accordingly.

This utility is extremely useful for modernizing older Node.js codebases that rely heavily on callbacks. By converting these callback-style functions to Promises, developers can avoid callback hell and write more sequential and easier-to-understand asynchronous code. It integrates seamlessly with the Promise API and is a cornerstone for leveraging async/await. For example, if you have a function like fs.readFile that uses callbacks, util.promisify(fs.readFile) would return a new function that returns a Promise, which can then be used with await.