如何在 JavaScript 中以程式設計方式模擬按鍵？

var keyboardEvent = document.createEvent('KeyboardEvent');
var initMethod = typeof keyboardEvent.initKeyboardEvent !== 'undefined' ? 'initKeyboardEvent' : 'initKeyEvent';

keyboardEvent[initMethod](
  'keydown', // event type: keydown, keyup, keypress
  true, // bubbles
  true, // cancelable
  window, // view: should be window
  false, // ctrlKey
  false, // altKey
  false, // shiftKey
  false, // metaKey
  40, // keyCode: unsigned long - the virtual key code, else 0
  0, // charCode: unsigned long - the Unicode character associated with the depressed key, else 0
);
document.dispatchEvent(keyboardEvent);