node.js fork example --> parent/child process increment and interchange the count variable until >100

child.js

const fork = require('child_process').fork;
const child = fork(require('path').join(__dirname, 'grand-child.js'));
new Promise(r => child.once('message', r)).then(c => process.send(c));
child.on('exit', process.exit);

var count =Math.floor(Math.random()*100);

process.on('message', async (msg)=>{

  console.log("CHILD: message received from parent process", msg);

  count = parseInt(msg) +1;
  console.log("CHILD: +1 from child");

  child.send(count);
  count = await new Promise(r => child.once('message', r));

  if(count<=100)
    process.send(count);
  else
    process.exit(1);

});

grand-child.js

var count = 0;
process.on('message', (msg)=>{

  console.log("GRAND-CHILD: message received from parent process", msg);

  count = parseInt(msg) +1;
  console.log("GRAND-CHILD: +1 from child");

  if (count <= 100)
    process.send(count);
  else
    process.exit(1);

});

console.log('gc', count);
process.send(count);

index.js

/** spawn example # spawn will not create new V8 instance, it will create a system process*/ 

/*
const spawn = require('child_process').spawn;

const ls = spawn("cmd", ['/c', '..']);

ls.stdout.on('data', (data)=>{

	console.log(process.pid);
	console.log(`stdout: ${data}`);	

});

ls.stderr.on('data', (data)=>{

	console.log(`stderr: ${data}`);

});

ls.on('message', (msg)=>{

 console.log(`message from child process is ${msg}`);

}); */

const fork = require('child_process').fork;

const child = fork(require('path').join(__dirname, 'child.js'));


var count =0;

child.on('exit', (code) => {
	console.log(`child_process exited with code ${code}`);
});

child.on('message', (msg)=>{

	 console.log(`PARENT: message from child process is ${msg}`);

	 count = parseInt(msg) + 1;
	 console.log("PARENT: +1 from parent");

	 child.send(count);

});