How to use the app.on function in app

// 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.
var mainWindow = null;

// 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();
  }
});

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
app.on('ready', function() {

  function requestHandler(req, res) {
    var
    file    = req.url == '/' ? '/app.html' : req.url,
    root    = __dirname + '/',
    page404 = root + '/404.html';
    console.log((root + file))
    getFile((root + file), res, page404);
  };

  // start a simple server that can serve an html page and resolve local file loading.
  var server = http.createServer(requestHandler).listen(3000);

  // Put the app on a secondary display if availalbe
  var atomScreen = require('screen');
  var displays = atomScreen.getAllDisplays();

// Report crashes to our server.
require('crash-reporter').start();

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the javascript object is GCed.
var mainWindow = null;

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

// This method will be called when Electron has done everything
// initialization and ready for creating browser windows.
app.on('ready', function() {

  // Register a 'ctrl+x' shortcut listener.
  var ret = globalShortcut.register(process.platform === 'win32' ? 'ctrl+g' : 'cmd+g', function() {
    console.log('cmd+g/ctrl+g is pressed');
    console.log(clipboard.readText('selection'));
    var url = clipboard.readText('selection');
    mainWindow.webContents.executeJavaScript("addNewURL('"+url+"');");
  });

  if (!ret) {
    console.log('registration failed');
  }


  if (app.dock) app.dock.hide();

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the javascript object is GCed.
var mainWindow = null;

// Quit when all windows are closed.
app.on('window-all-closed', function() {
  app.quit();
});

var Menu = require('menu');



// This method will be called when Electron has done everything
// initialization and ready for creating browser windows.
app.on('ready', function() {
    initWindow();

    function initWindow () {
        // Create the browser window.
        mainWindow = new BrowserWindow({width: 1058, height: 640, resizable: false});

        // and load the index.html of the app.
        mainWindow.loadUrl(hosturl + '#/setup')

        // 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;
        });

onNext = function (data) {
        modeNext += 1;
        switch (modeNext) {
        case 1:
            /* istanbul ignore next */
            if (process.env.npm_config_mode_auto_restart) {
                return;
            }
            // wait for electron to init
            try {
                require("app").on("ready", onNext);
            } catch (ignore) {
                require("electron").app.once("ready", onNext);
            }
            break;
        case 2:
            // init options
            options = {
                frame: false,
                height: 768,
                width: 1024,
                x: 0,
                y: 0
            };
            // init browserWindow;
            try {
                options.BrowserWindow = require("browser-window");

var target = path.basename(process.execPath);
  switch (squirrelCommand) {
    case "--squirrel-install":
    case "--squirrel-updated":
      updateCmd(["--createShortcut", target], app.quit);
      break;
    case "--squirrel-uninstall":
      updateCmd(["--removeShortcut", target], app.quit);
      break;
    case "--squirrel-obsolete":
      app.quit();
      break;
  }
}

app.on("ready", function() {
  var appIcon = new Tray(iconIdle);
  initWindow();

  if (process.platform === "darwin") {
    applySettings();
  }

  function initWindow() {
    var defaults = {
      frame: false,
      height: 600,
      resizable: false,
      width: 360
    };

    appIcon.window = new BrowserWindow(defaults);