NodeJS

[anitsh]

NodeJS

Key Points

• Each file is treated as a separate module.

Resource https://trello.com/c/rZ0k1i51/798-nodejs

Basics, Architecture

• [ ] https://docs.microsoft.com/en-gb/learn/modules/intro-to-nodejs
• [ ] https://nodejs.dev/learn
• [ ] https://developers.redhat.com/blog/2021/03/08/introduction-to-the-node-js-reference-architecture-part-1-overview
• [ ] https://node-tap.org/docs/getting-started
• [ ] https://github.com/googleapis/google-api-nodejs-client

  Monitoring, Security, Tools

• [ ] https://blog.risingstack.com/node-js-performance-monitoring-with-prometheus
• [ ] https://snyk.io/blog/ten-npm-security-best-practices
• [ ] https://www.bleepingcomputer.com/news/security/heavily-used-nodejs-package-has-a-code-injection-vulnerability
• [ ] https://portswigger.net/daily-swig/ssrf-vulnerability-in-npm-package-netmask-impacts-up-to-279k-projects
• [ ] https://github.com/google/zx

[anitsh]

Module

Functions exported as module

---

foo.js

const circle = require('./circle.js');
console.log(`The area of a circle of radius 4 is ${circle.area(4)}`);

circle.js:

const { PI } = Math;
exports.area = (r) => PI * r ** 2;
exports.circumference = (r) => 2 * PI * r;

---

Class exported as module

bar.js

const Square = require('./square.js');
const mySquare = new Square(2);
console.log(`The area of mySquare is ${mySquare.area()}`);

square.js:

module.exports = class Square {
  constructor(width) {
    this.width = width;
  }
  area() {
    return this.width ** 2;
  }
};

---

When a file is run directly from Node.js, require.main is set to its module. That means that it is possible to determine whether a file has been run directly by testing require.main === module.

For a file foo.js, this will be true if run via node foo.js, but false if run by require('./foo').

Because module provides a filename property (normally equivalent to __filename), the entry point of the current application can be obtained by checking require.main.filename.

Resource

• https://nodejs.org/api/modules.html Modules: CommonJS modules
• https://nodejs.org/api/esm.html https://nodejs.org/api/esm.html
• https://nodejs.org/api/module.html Modules: module API
• https://nodejs.org/api/documentation.html
• https://nodejs.org/api/packages.html Packages