Error fix: module ‘require’ not defined/found & similar errors - NodeJS

When running a nodejs project on my computer, I ran into a similar error to the one below:

var express = require('express');
              ^
              
ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and '/home/ismael/Projects/private-website-blocker/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.

After some research, it turns out that I had ESM (ECMAScript modules) enabled in my package.json file.

//package.json
{
    "type": "module"
    ...
}

To fix this problem, I either needed to use CommonJS modules and remove "type": "module" from package.json or use ECMAScript modules and use ES6 syntax. Although I could use both, I chose the latter option to make things simple and consistent. To transition to ES6 syntax, I made changes to my code similar to the following example:

From:

const express = require('express');

exports.myExport = 7 * 3;

module.exports = class MyClass {
    ...
}

To:

import express from 'express';

export const myExport = 7 * 3;

export class MyClass {
    ...
}