setTimeout(() => console.log("timeout"));
 
Promise.resolve()
  .then(() => console.log("promise"));
  
console.log("main");

function logA() { console.log('A') };
function logB() { console.log('B') };
function logC() { console.log('C') };
function logD() { console.log('D') };
function logE() { console.log('E') };
function logF() { console.log('F') };
function logG() { console.log('G') };
function logH() { console.log('H') };
function logI() { console.log('I') };
function logJ() { console.log('J') };
 
logA();
setTimeout(logG, 0);
Promise.resolve()
  .then(logC)
  .then(setTimeout(logH))
  .then(logD)
  .then(logE)
  .then(logF);
setTimeout(logI);
setTimeout(logJ);
logB();

const messageQueue = [];
 
let sendMessage = message => {
  messageQueue.push(message);
 
  if (messageQueue.length === 1) {
    queueMicrotask(() => {
      const json = JSON.stringify(messageQueue);
      messageQueue.length = 0;
      fetch("url-of-receiver", json);
    });
  }
};

console.log(1)
setTimeout(() => {
    queueMicrotask(() => {
       console.log(2)
     });
  console.log(3)
});
Promise.resolve().then(() => console.log(4))
queueMicrotask(() => {
    console.log(5)
    queueMicrotask(() => {
        console.log(6)
    });
});
console.log(7)

console.log('Start')
 
setImmediate(() => console.log('Queued using setImmediate'))
 
console.log('End')

setTimeout(() => {
  console.log('timeout');
}, 0);
 
setImmediate(() => {
  console.log('immediate');
});

console.log('Start')
 
process.nextTick(() => console.log('Queued using process.nextTick'))
 
console.log('End')

Promise.resolve().then(() => { console.log('1'); });
 
process.nextTick(() => {
  console.log('2.');
  process.nextTick(() => {
    console.log('3');
    process.nextTick(() => {
      console.log('3');
      process.nextTick(() => {
        console.log('5');
      })
    })
  })
})

let count = 0
 
const cb = () => {
    console.log(`Processing setImmediate cb ${++count}`)
    setImmediate(cb)
}
 
setImmediate(cb)
setTimeout(() => console.log('setTimeout executed'), 100)
 
console.log('Start')

const express = require("express")
 
const app = express()
app.get("/getfibonacci", (req, res) => {
  const startTime = new Date()
  const result = fibonacci(parseInt(req.query.number)) //parseInt is for converting string to number
  const endTime = new Date()
  res.json({
    number: parseInt(req.query.number),
    fibonacci: result,
    time: endTime.getTime() - startTime.getTime() + "ms",
  })
})
const fibonacci = n => {
  if (n <= 1) {
    return 1
  }
  return fibonacci(n - 1) + fibonacci(n - 2)
}
app.listen(3000, () => console.log("listening on port 3000"))

const express = require("express")
const app = express()
const { fork } = require("child_process")
 
app.get("/isprime", (req, res) => {
  const childProcess = fork("./forkedchild.js") //the first argument to fork() is the name of the js file to be run by the child process
  childProcess.send({ number: parseInt(req.query.number) }) //send method is used to send message to child process through IPC
  const startTime = new Date()
  childProcess.on("message", message => {
    //on("message") method is used to listen for messages send by the child process
    const endTime = new Date()
    res.json({
      ...message,
      time: endTime.getTime() - startTime.getTime() + "ms",
    })
  })
})
 
 
// child.js
// 
 
 
process.on("message", message => {
  //child process is listening for messages by the parent process
  const result = isPrime(message.number)
  process.send(result)
  process.exit() // make sure to use exit() to prevent orphaned processes
})
function isPrime(number) {
  let isPrime = true
  for (let i = 3; i < number; i++) {
    if (number % i === 0) {
      isPrime = false
      break
    }
  }
  return {
    number: number,
    isPrime: isPrime,
  }
}

const {
  Worker, isMainThread, parentPort, workerData
} = require('worker_threads');
 
if (isMainThread) {
  module.exports = function parseJSAsync(script) {
    return new Promise((resolve, reject) => {
      const worker = new Worker(__filename, {
        workerData: script
      });
      worker.on('message', resolve);
      worker.on('error', reject);
      worker.on('exit', (code) => {
        if (code !== 0)
          reject(new Error(`Worker stopped with exit code ${code}`));
      });
    });
  };
} else {
  const { parse } = require('some-js-parsing-library');
  const script = workerData;
  parentPort.postMessage(parse(script));
}

import { parentPort } from 'worker_threads';
parentPort.on('message', () => {
 const numberOfElements = 100;
 const sharedBuffer = new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * numberOfElements);
 const arr = new Int32Array(sharedBuffer);
 for (let i = 0; i < numberOfElements; i += 1) {
   arr[i] = Math.round(Math.random() * 30);
 }
 parentPort.postMessage({ arr });
});

const cluster = require("cluster")
const http = require("http")
const cpuCount = require("os").cpus().length //returns no of cores our cpu have
if (cluster.isMaster) {
  masterProcess()
} else {
  childProcess()
}
function masterProcess() {
  console.log(`Master process ${process.pid} is running`)
  //fork workers.
  for (let i = 0; i < cpuCount; i++) {
    console.log(`Forking process number ${i}...`)
    cluster.fork() //creates new node js processes
  }
  cluster.on("exit", (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`)
    cluster.fork() //forks a new process if any process dies
  })
}
function childProcess() {
  const express = require("express")
  const app = express()
  //workers can share TCP connection
  app.get("/", (req, res) => {
    res.send(`hello from server ${process.pid}`)
  })
  app.listen(5555, () =>
    console.log(`server ${process.pid} listening on port 5555`)
  )
}