const {app, BrowserWindow} = require('electron')
const path = require('path')
const url = require('url')

let mainWindow

function createWindow() {
  mainWindow = new BrowserWindow({
                  width: 800,
                  height: 600
                })
  
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'index.html'),
    protocol: 'file:',
    slashes: true
  }))
  
  mainWindow.on('closed', () => {
    mainWindow = null
  })
}

app.on('ready', createWindow)

app.on('window-all-closed', () => {
  if (process.platform !== 'darwin') {
    app.quit() 
  }
})

app.on('activate', () => {
  if (mainWindow === null) {
    createWindow() 
  }
})

const {app, BrowserWindow} = require('electron')
const path = require('path')
const url = require('url')

let mainWindow

function createWindow() {
  mainWindow = new BrowserWindow({
    width: 800,
    height: 600
  })
  
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, '../public/index.html'),
    protocol: 'file:',
    slashes: true
  }))
  
  mainWindow.on('closed', () => {
    mainWindow = null
  })
}

app.on('ready', createWindow)

app.on('window-all-closed', () => {
  if (process.platform !== 'darwin') {
    app.quit() 
  }
})

app.on('activate', () => {
  if (mainWindow === null) {
    createWindow() 
  }
})

Update main.js