NodeJS provides a utility function called promisify which can be used to convert the callback function to promise. The promise is more readable and easier to handle using a promise. There are many npm packages available that can be. used to. convert callback to promise without using any. any. npm package. I will show you how to convert. to promise using a simple add function that will take a. callback function as a parameter and return the promise. A promise is used to handle multiple.