title: Electron set fullscreen onclick
body: <p>I am trying to make app window fullscreen on click but get following error <code>main.js:29 Uncaught TypeError: Cannot read property 'setFullScreen' of undefined</code></p>
  
  <p><strong>main.js</strong> </p>
  
  <pre><code>    const electron = require('electron')
  // Module to control application life.
  const app = electron.app
  // Module to create native browser window.
  const BrowserWindow = electron.BrowserWindow
  
  // 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
  
  function createWindow () {
    // Create the browser window.
    mainWindow = new BrowserWindow({width: 1200, height: 600})
  
    // and load the index.html of the app.
    mainWindow.loadURL(`file://${__dirname}/index.html`)
    // 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
    })
  }
  
  function toggleFullScreen() {
    mainWindow.setFullScreen(true)
  }
  </code></pre>