process.on('disconnect', () => {
    // Disconnect event
});

// Require fork method from child_process  
// to spawn child process 
const fork = require('child_process').fork; 
    
// Child process file 
const child_file = 'child.js'; 
    
// Spawn child process 
const child = fork(child_file);

console.log('In child.js') 
  
if (process.connected) { 
    console.log("Child Process connected!") 
    console.log("Disconnecting in 3000ms") 
    setTimeout(() => { 
        process.disconnect(); 
    }, 3000); 
} 
  
process.on('disconnect', () => { 
    console.log("Child Process disconnected!") 
});

In child.js
Child Process connected!
Disconnecting in 3000ms 
Child Process disconnected!

// Require fork method from child_process  
// to spawn child process 
const fork = require('child_process').fork; 
    
// Child process file 
const child_file = 'child2.js'; 
    
// Spawn child process 
const child = fork(child_file);

console.log("In Child Process!") 
  
process.disconnect() 
  
process.on('disconnect', () => { 
    console.log(`Child process disconnected`); 
});

In Child Process!
Child process disconnected