util

format

Formats a string using placeholders and returns it. Similar to printf in C.

const util = require('util');
console.log(util.format('%s:%s', 'foo', 'bar', 'baz')); // 'foo:bar baz'

inspect

Returns a string representation of an object for debugging purposes, with options to show hidden properties and control the depth of inspection.

const util = require('util');
console.log(util.inspect({ foo: 'bar' }, { showHidden: false, depth: null }));

inherits

Allows one constructor to inherit the prototype methods from another, a utility for implementing object-oriented inheritance.

const util = require('util');
function Base() {}
function Derived() {}
util.inherits(Derived, Base);

promisify

Converts a callback-based function to a function that returns a promise, facilitating the use of async/await.

const util = require('util');
const fs = require('fs');
const readFileAsync = util.promisify(fs.readFile);
readFileAsync('example.txt', 'utf8').then(console.log).catch(console.error);