keyboard-event.js

var NativeKeyboardEvent = window.KeyboardEvent || function() {};

// IE8KeyboardEvent
var IE8KeyboardEvent = function(eventType, args) {
  args = normalizeArgs(args);
  var evt = document.createEventObject();

  evt.type = eventType;
  evt.key = args.key;
  evt.keyCode = args.key;
  evt.ctrlKey = args.ctrlKey;
  evt.shiftKey = args.shiftKey;
  evt.altKey = args.altKey;
  evt.repeat = args.repeat;

  return evt;
};
IE8KeyboardEvent.type = 'IE8';

// DL3KeyboardEvent
var DL3KeyboardEvent = function(eventType, args) {
  // chrome polyfill
  if (args && args.key) {
    args.keyIdentifier = args.key;
  }

  args = normalizeArgs(args);
  var evt = document.createEvent('KeyboardEvent');
  var modifiers = modifiersList(args);

  evt.initKeyboardEvent(eventType, args.bubbles, args.cancelable, null,
    args.key, args.location, modifiers, args.repeat, args.locale);

  // chrome polyfill
  if (evt.keyIdentifier && evt.key !== evt.keyIdentifier) {
    evt.key = evt.keyIdentifier;
  }

  return evt;
};
DL3KeyboardEvent.prototype = Object.create(NativeKeyboardEvent.prototype);
DL3KeyboardEvent.prototype.constructor = DL3KeyboardEvent;

// DL4KeyboardEvent
var DL4KeyboardEvent = function(eventType, args) {
  // chrome polyfill
  if (args && args.key) {
    args.keyIdentifier = args.key;
  }

  var evt = new NativeKeyboardEvent(eventType, args);

  // chrome polyfill
  if (evt.keyIdentifier && evt.key !== evt.keyIdentifier) {
    evt.key = evt.keyIdentifier;
  }

  return evt;
};
DL4KeyboardEvent.prototype = Object.create(NativeKeyboardEvent.prototype);
DL4KeyboardEvent.prototype.constructor = DL4KeyboardEvent;

// Polyfilling
if (document.implementation.hasFeature('KeyboardEvent', '4.0')) {
  KeyboardEvent = DL4KeyboardEvent;
}
else if (document.implementation.hasFeature('KeyboardEvent', '3.0')) {
  KeyboardEvent = DL3KeyboardEvent;
}
else if (document.createEventObject) {
  KeyboardEvent = IE8KeyboardEvent;
}
else if (navigator.userAgent.indexOf('PhantomJS') !== -1) {
  // seems to support DL3 keyboard events even though it doesn't claim to
  KeyboardEvent = DL3KeyboardEvent;
}
else {
  throw new Error('keyboard-event polyfill unable to shim browser.');
}

// Private Functions
function normalizeArgs(args) {
  args = args || {};
  args.bubbles = defaultsTo(false, args.bubbles);
  args.cancelable = defaultsTo(false, args.cancelable);
  args.location = defaultsTo(0, args.location);
  args.repeat = defaultsTo(false, args.repeat);
  args.locale = defaultsTo('', args.locale);
  args.ctrlKey = defaultsTo(false, args.ctrlKey);
  args.shiftKey = defaultsTo(false, args.shiftKey);
  args.altKey = defaultsTo(false, args.altKey);
  args.metaKey = defaultsTo(false, args.metaKey);

  return args;
}

function defaultsTo(defaultValue, actualValue) {
  return (actualValue === undefined) ? defaultValue : actualValue;
}

function modifiersList(args) {
  var modifiers = [];

  if (args.ctrlKey) {
    modifiers.push('Control');
  }
  if (args.shiftKey) {
    modifiers.push('Shift');
  }
  if (args.altKey) {
    modifiers.push('Alt');
  }
  if (args.metaKey) {
    modifiers.push('Meta');
  }
  if (args.ctrlKey && args.altKey) {
    modifiers.push('AltGraph');
  }

  return modifiers.join(' ');
}