how to make process run in background in Node JS ?

const cluster = require('cluster');

const electron = require('electron')
const cluster = require('cluster');
const numCPUs = require('os').cpus().length
const app = electron.app
// Module to create native browser window.
const BrowserWindow = electron.BrowserWindow

const path = require('path')
const url = require('url')

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

  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  cluster.on('exit', (worker, code, signal) => {
    console.log(`worker ${worker.process.pid} died`);
  });
} else {
// Module to control application life.


// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the JavaScript object is garbage collected.
let mainWindow

function createWindow () {
  // Create the browser window.
  mainWindow = new BrowserWindow({width: 800, height: 600})

  // and load the index.html of the app.
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'index.html'),
    protocol: 'file:',
    slashes: true
  }))

  // Open the DevTools.
  // mainWindow.webContents.openDevTools()

  // Emitted when the window is closed.
  mainWindow.on('closed', function () {
    // Dereference the window object, usually you would store windows
    // in an array if your app supports multi windows, this is the time
    // when you should delete the corresponding element.
    mainWindow = null
  })
}
// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.

app.on('ready', createWindow)

// Quit when all windows are closed.

app.on('window-all-closed', function () {
  // On OS X it is common for applications and their menu bar
  // to stay active until the user quits explicitly with Cmd + Q
  if (process.platform !== 'darwin') {
    app.quit()
  }
})

app.on('activate', function () {
  // On OS X it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (mainWindow === null) {
    createWindow()
  }
})
}
// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

[sudo] npm install forever

 forever start server.js

 forever list