index.js

const electron = require('electron');
const app = electron.app;
const BrowserWindow = electron.BrowserWindow;
let mainWindow = null;

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

app.on('ready', function() {
  mainWindow = new BrowserWindow({width: 800, height: 600});
  mainWindow.loadURL('https://twitter.com');

  mainWindow.on('closed', function() {
    mainWindow = null;
  });
});