Advanced NodeJS

async.js

const https = require('https');

process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';

const start = Date.now();

function doRequest() {
  https.request('https://www.google.com', res => {
    res.on('data', () => {})
    res.on('end', () => {
      console.log(Date.now() - start)
    })
  })
  .end();
}

doRequest();
doRequest();
doRequest();
doRequest();
doRequest();

event-loop.js

// node myFile.js

const pendingTimers = [];
const pendingOSTasks = [];
const pendingOperations = [];

// New timers, tasks, operations are recorded from myFile running
myFile.runContents();

function shouldContinue() {
  // Check one: Any pending setTimeout, setInterval, setImmediate?
  // Check two: Any pending OS tasks? (Like server listening to port)
  // Check three: Any pending long running operations? (Like fs module)
  return pendingTimers.length || pendingOSTasks.length || pendingOperations.length;
}

// Entire body executes in one 'tick'
while(shouldContinue()) {
  // 1) Node looks at pendingTimers and sees if any functions are ready to be called. setTimeout, setInterval

  // 2) Node looks at pendingOSTasks and pendingOperations and calls relevant callbacks

  // 3) Pause execution. Continue when...
  // - a new pendingOSTask is done
  // - a new pendingOperation is done
  // - a timer is about to complete

  // 4) Look at pendingTimers. Call any setImmediate

  // 5) Handle any 'close' events
}

// exit back to terminal

threads.js

const crypto = require('crypto');

const start = Date.now();

crypto.pbkdf2('a', 'b', 100000, 512, 'sha512', () => {
  console.log('1:', Date.now() - start);
});

crypto.pbkdf2('a', 'b', 100000, 512, 'sha512', () => {
  console.log('2:', Date.now() - start);
});

crypto.pbkdf2('a', 'b', 100000, 512, 'sha512', () => {
  console.log('3:', Date.now() - start);
});

crypto.pbkdf2('a', 'b', 100000, 512, 'sha512', () => {
  console.log('4:', Date.now() - start);
});

crypto.pbkdf2('a', 'b', 100000, 512, 'sha512', () => {
  console.log('5:', Date.now() - start);
});