NodeJS Cheat Sheet

1. Install NodeJS


sudo apt-get install nodejs

2. Check NodeJS Version


node -v

3. Create a New NodeJS Project


npm init

4. Install Dependencies


npm install express

5. Create a New NodeJS File


touch app.js

6. Run a NodeJS File


node app.js

7. Use the `require` Function


const express = require('express');

8. Use the `module.exports` Object


module.exports = function() {
  console.log('Hello, World!');
};

9. Use the `console.log` Function


console.log('Hello, World!');

10. Use the `process` Object


console.log(process.argv);

11. Use the `fs` Module


const fs = require('fs');
fs.readFile('file.txt', 'utf8', (err, data) => {
  console.log(data);
});

12. Use the `http` Module


const http = require('http');
http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello, World!\n');
}).listen(3000, () => {
  console.log('Server running on port 3000');
});

13. Use the `https` Module


const https = require('https');
https.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello, World!\n');
}).listen(3000, () => {
  console.log('Server running on port 3000');
});

14. Use the `path` Module


const path = require('path');
console.log(path.join('path', 'to', 'file'));

15. Use the `url` Module


const url = require('url');
console.log(url.parse('https://example.com/path/to/resource'));

16. Use the `querystring` Module


const querystring = require('querystring');
console.log(querystring.parse('key=value&foo=bar'));

17. Use the `punycode` Module


const punycode = require('punycode');
console.log(punycode.encode('example.com'));

18. Use the `dns` Module


const dns = require('dns');
dns.lookup('example.com', (err, address) => {
  console.log(address);
});

19. Use the `net` Module


const net = require('net');
const server = net.createServer((socket) => {
  socket.on('data', (data) => {
    console.log(data.toString());
  });
});
server.listen(3000, () => {
  console.log('Server running on port 3000');
});

20. Use the `dgram` Module


const dgram = require('dgram');
const server = dgram.createSocket('udp4');
server.on('message', (msg, rinfo) => {
  console.log(msg.toString());
});
server.bind(3000, () => {
  console.log('Server running on port 3000');
});

21. Use the `child_process` Module


const childProcess = require('child_process');
const child = childProcess.spawn('ls', ['-l']);
child.stdout.on('data', (data) => {
  console.log(data.toString());
});

22. Use the `cluster` Module


const cluster = require('cluster');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);

  for (let i = 0; i < num CPUs; i++) {
    cluster.fork();
  }
} else {
  require('./app.js');
  console.log(`Worker ${process.pid} started`);
}

23. Use the `events` Module


const EventEmitter = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {
  console.log('An event occurred!');
});
myEmitter.emit('event');

24. Use the `stream` Module


const { Readable } = require('stream');
const readable = new Readable({
  read() {
    this.push('Hello, World!');
    this.push(null);
  }
});
readable.pipe(process.stdout);

25. Use the `buffer` Module


const buf = Buffer.from('Hello, World!');
console.log(buf.toString());

26. Use the `os` Module


const os = require('os');
console.log(os.platform());

27. Use the `crypto` Module


const crypto = require('crypto');
const hash = crypto.createHash('sha256');
hash.update('Hello, World!');
console.log(hash.digest('hex'));

28. Use the `zlib` Module


const zlib = require('zlib');
const input = 'Hello, World!';
const buffer = Buffer.from(input);
zlib.deflate(buffer, (err, buffer) => {
  console.log(buffer.toString('base64'));
});

29. Use the `vm` Module


const vm = require('vm');
const script = new vm.Script('console.log("Hello from VM!");');
script.runInThisContext();

30. Use the `timers` Module


const timers = require('timers');
timers.setTimeout(() => {
  console.log('Executed after 1 second');
}, 1000);

31. Use the `readline` Module


const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});
rl.question('What is your name? ', (answer) => {
  console.log(`Hello, ${answer}!`);
  rl.close();
});

32. Use the `assert` Module


const assert = require('assert');
assert.strictEqual(1, 1, 'Values are not equal');

33. Use the `util` Module


const util = require('util');
const promisified = util.promisify(setTimeout);
promisified(1000).then(() => console.log('Executed after 1 second'));

34. Use the `http2` Module


const http2 = require('http2');
const server = http2.createServer((req, res) => {
  res.writeHead(200);
  res.end('Hello, World!');
});
server.listen(3000);

35. Use the `inspector` Module


const inspector = require('inspector');
inspector.open(9229, null, true);
console.log('Inspector is running on port 9229');

36. Use the `module` Object


console.log(module.filename);

37. Use the `global` Object


global.myGlobalVar = 'Hello, World!';
console.log(global.myGlobalVar);

38. Use the `this` Keyword


console.log(this);

39. Use the `__dirname` Variable


console.log(__dirname);

40. Use the `__filename` Variable


console.log(__filename);

41. Use the `npm` Command


npm install <package-name>

42. Use the `npx` Command


npx create-react-app my-app

43. Use the `npm start` Command


npm start

44. Use the `npm test` Command


 npm test

45. Use the `npm run` Command


npm run <script-name>

46. Use the `npm install --save` Command


npm install --save <package-name>

47. Use the `npm install --save-dev` Command


npm install --save-dev <package-name>

48. Use the `npm uninstall` Command


npm uninstall <package-name>

49. Use the `npm update` Command


npm update

50. Use the `npm outdated` Command


npm outdated

51. Use the `npm init -y` Command


npm init -y

52. Use the `npm config` Command


npm config set <key> <value>

53. Use the `npm cache` Command


npm cache clean --force

54. Use the `npm link` Command


npm link <package-name>

55. Use the `npm audit` Command


npm audit

56. Use the `npm audit fix` Command


npm audit fix

57. Use the `npm run build` Command


npm run build

58. Use the `npm run dev` Command


npm run dev

59. Use the `npm run lint` Command


npm run lint

60. Use the `npm run test` Command


npm run test

61. Use the `npm run format` Command


npm run format

62. Use the `npm run serve` Command


npm run serve

63. Use the `npm run watch` Command


npm run watch

64. Use the `npm run clean` Command


npm run clean

65. Use the `npm run deploy` Command


npm run deploy

66. Use the `npm run prestart` Command


npm run prestart

67. Use the `npm run postinstall` Command


npm run postinstall

68. Use the `npm run pretest` Command


npm run pretest

69. Use the `npm run posttest` Command


npm run posttest

70. Use the `npm run prebuild` Command


npm run prebuild

71. Use the `npm run postbuild` Command


npm run postbuild

72. Use the `npm run predeploy` Command


npm run predeploy

73. Use the `npm run postdeploy` Command


npm run postdeploy

74. Use the `npm run preformat` Command


npm run preformat

75. Use the `npm run postformat` Command


npm run postformat

76. Use the `npm run prelint` Command


npm run prelint

77. Use the `npm run postlint` Command


npm run postlint

78. Use the `npm run prewatch` Command


npm run prewatch

79. Use the `npm run postwatch` Command


npm run postwatch

80. Use the `npm run preclean` Command


npm run preclean

81. Use the `npm run postclean` Command


npm run postclean

82. Use the `npm run preinstall` Command


npm run preinstall

83. Use the `npm run postinstall` Command


npm run postinstall

84. Use the `npm run preuninstall` Command


npm run preuninstall

85. Use the `npm run postuninstall` Command


npm run postuninstall

86. Use the `npm run preupdate` Command


npm run preupdate

87. Use the `npm run postupdate` Command


npm run postupdate

88. Use the `npm run prewatch` Command


npm run prewatch

89. Use the `npm run postwatch` Command


npm run postwatch

90. Use the `npm run pretest` Command


npm run pretest

91. Use the `npm run posttest` Command


npm run posttest

92. Use the `npm run prebuild` Command


npm run prebuild

93. Use the `npm run postbuild` Command


npm run postbuild

94. Use the `npm run predeploy` Command


npm run predeploy

95. Use the `npm run postdeploy` Command


npm run postdeploy

96. Use the `npm run preformat` Command


npm run preformat

97. Use the `npm run postformat` Command


npm run postformat

98. Use the `npm run prelint` Command


npm run prelint

99. Use the `npm run postlint` Command


npm run postlint

100. Use the `npm run prewatch` Command


npm run prewatch