Node.js encompasses a range of components that come together to form a JavaScript runtime environment. In our series on Node.js Architecture - Introduction to Node.js, we explored the various components that make up Node.js and their respective functions.
Within Node.js, there are numerous built-in modules - i.e., modules that are integrated from the outset. One such module is util
, which, in my opinion, deserves more attention. The util
module comprises a collection of small utility functions that can be helpful in certain situations. In this article, we will delve into some of these functions...
The callback is one of the earliest ways to handle asynchronous code. However, callbacks have several limitations, such as creating nested code and causing the infamous "callback hell." Occasionally, reading a piece of code written in a callback style can be overwhelming. Adding new functionality can be challenging, as it requires introducing an additional layer of logic.
In Node.js, there is a utility function to convert asynchronous functions using the callback style to Promises. This function is useful when you want to transition to a Promise-based approach and then combine it with async/await to make your code more concise and easier to follow.
const util = require('node:util');
const fs = require('node:fs');
const stat = util.promisify(fs.stat);
async function callStat() {
const stats = await stat('.');
console.log(`This directory is owned by ${stats.uid}`);
}
callStat();
Conversely, we have util.callbackify
to convert Promise-based functions back to callbacks.
const util = require('node:util');
async function fn() {
return 'hello world';
}
const callbackFunction = util.callbackify(fn);
callbackFunction((err, ret) => {
if (err) throw err;
console.log(ret);
});
If you frequently use libraries, you may have noticed console messages indicating that a function is deprecated.
oldFunction() is deprecated. Use newFunction() instead.
This is a notification that the oldFunction
is nearing the end of its support lifecycle and may be removed in the future. It is a common approach to remind developers that a function is approaching its "retirement" and to use an alternative function instead.
In Node.js, there is a simple way to display this notification if you need to warn others that a function is nearing its end-of-life.
const util = require('util');
function oldFunction() {
console.log('This function is deprecated!');
}
const deprecatedFunction = util.deprecate(oldFunction, 'oldFunction() is deprecated. Use newFunction() instead.');
Simply "wrap" the oldFunction
inside util.deprecate
. Each time oldFunction
is called, the warning message will appear in the console.
From ES6 onward, we have additional functions to check the type of data: boolean, array, object, etc.
The util
module has a types
property that extends the capability to check data types.
For instance:
console.log(util.types.isPromise(Promise.resolve())); // true
console.log(util.types.isRegExp(/abc/)); // true
console.log(util.types.isDate(new Date())); // true
A comprehensive list is available at util.types | Node.js documentation.
isDeepStrictEqual
is the most efficient method to compare two objects and determine if they are identical.
const util = require('util');
const obj1 = { a: 1, b: { c: 2 } };
const obj2 = { a: 1, b: { c: 2 } };
console.log(util.isDeepStrictEqual(obj1, obj2)); // true
In addition to these functions, the util
module provides many other utility functions, such as util.styleText
to format text output in the console, and util.parseEnv
to parse the contents of environment variables in .env
files.
For more information, refer to:
5 profound lessons
Every product comes with stories. The success of others is an inspiration for many to follow. 5 lessons learned have changed me forever. How about you? Click now!
Subscribe to receive new article notifications
Hello, my name is Hoai - a developer who tells stories through writing ✍️ and creating products 🚀. With many years of programming experience, I have contributed to various products that bring value to users at my workplace as well as to myself. My hobbies include reading, writing, and researching... I created this blog with the mission of delivering quality articles to the readers of 2coffee.dev.Follow me through these channels LinkedIn, Facebook, Instagram, Telegram.
Comments (0)