electron.js

const electron = require('electron')
const app = electron.app
const BrowserWindow = electron.BrowserWindow

const path = require('path')
const isDev = require('electron-is-dev')

let mainWindow

function createWindow() {
  mainWindow = new BrowserWindow({
    width: 358,
    height: 600,
    webPreferences: { preload: path.join(__dirname, 'preload.js') }
  })
  mainWindow.loadURL(
    isDev
      ? 'http://localhost:3001'
      : `file://${path.join(__dirname, './build/index.html')}`
  )

  if (isDev) {
    // Open the DevTools.
    //BrowserWindow.addDevToolsExtension('<location to your react chrome extension>');
    mainWindow.webContents.openDevTools()
  }
  mainWindow.on('closed', () => (mainWindow = null))
}

const restoreInstance = () => {
  mainWindow.show()
  if (mainWindow.isMinimized()) mainWindow.restore()
}

const activateInstance = e => {
  if (e) e.preventDefault()
  if (!mainWindow) {
    createWindow()
    return
  }
  restoreInstance()
}

app.on('ready', createWindow)

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

app.on('activate', activateInstance)