main.js

const electron = require('electron');
// Module to control application life.
const app = electron.app;
// Module to create native browser window.
const BrowserWindow = electron.BrowserWindow;

const path = require('path');
const url = require('url');
const {session, ipcMain} = require('electron');

// 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;
let login=false;
let id='';
const template = [
  {
    label: 'Upload',
    click () { 
      if(login){
        mainWindow.loadURL(url.format({
          pathname: path.join(__dirname, 'app/upload.html'),
          protocol: 'file:',
          slashes: true
          }));
      }
      else{
        mainWindow.loadURL(url.format({
          pathname: path.join(__dirname, 'app/login.html'),
          protocol: 'file:',
          slashes: true
        }));
      }
    }
  },
  {
    label: 'Downlaod',
    click () { 
      mainWindow.loadURL(url.format({
      pathname: path.join(__dirname, 'app/download.html'),
      protocol: 'file:',
      slashes: true
      })); 
    }
  }
];
function createWindow () {
  // Create the browser window.
  mainWindow = new BrowserWindow({width: 800, height: 600, icon: path.join(__dirname, 'app/img/icon.png')});

  // and load the index.html of the app.
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'app/login.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;
  });
  const menu = electron.Menu.buildFromTemplate(template);
  mainWindow.setResizable(false);
  mainWindow.setMenu(menu);
}

// 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();
  }
});

ipcMain.on('login', (event, arg) => {
  id=arg;
  login=true;
});

ipcMain.on('upload', (event, arg) => {
  event.returnValue = id;
});

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.