main.js

// Modules to control application life and create native browser window
const {app, BrowserWindow} = require('electron')
const path = require('path')

function createWindow () {
  // Create the browser window.
  const mainWindow = new BrowserWindow({
    width: 800,
    height: 600,
    webPreferences: {
      preload: path.join(__dirname, 'preload.js')
    },
    /// show to false mean than the window will proceed with its lifecycle, but will not render until we will show it up
    show: false
  })

  // and load the index.html of the app.
  mainWindow.loadFile('index.html')

  /// keep listening on the did-finish-load event, when the mainWindow content has loaded
  mainWindow.webContents.on('did-finish-load', () => {
    /// then close the loading screen window and show the main window
    if (loadingScreen) {
      loadingScreen.close();
    }
    mainWindow.show();
  });

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

/// create a global var, wich will keep a reference to out loadingScreen window
let loadingScreen;
const createLoadingScreen = () => {
  /// create a browser window
  loadingScreen = new BrowserWindow(
    Object.assign({
      /// define width and height for the window
      width: 200,
      height: 400,
      /// remove the window frame, so it will become a frameless window
      frame: false,
      /// and set the transparency, to remove any window background color
      transparent: true
    })
  );
  loadingScreen.setResizable(false);
  loadingScreen.loadURL(
    'file://' + __dirname + '/windows/loading/loading.html'
  );
  loadingScreen.on('closed', () => (loadingScreen = null));
  loadingScreen.webContents.on('did-finish-load', () => {
    loadingScreen.show();
  });
};

// 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.whenReady().then(() => {
  createLoadingScreen();
  /// add a little bit of delay for tutorial purposes, remove when not needed
  setTimeout(() => {
    createWindow();
  }, 2000);
  
  app.on('activate', function () {
    // On macOS 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 (BrowserWindow.getAllWindows().length === 0) createWindow()
  })
})

// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

// 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.