71 lines
1.6 KiB
JavaScript
71 lines
1.6 KiB
JavaScript
|
/*
|
||
|
|
Copyright 2019 Google LLC
|
||
|
|
|
||
|
|
Use of this source code is governed by an MIT-style
|
||
|
|
license that can be found in the LICENSE file or at
|
||
|
|
https://opensource.org/licenses/MIT.
|
||
|
|
*/
|
||
|
|
|
||
|
|
import '../_version.mjs';
|
||
|
|
|
||
|
|
|
||
|
|
/**
|
||
|
|
* A minimal `EventTarget` shim.
|
||
|
|
* This is necessary because not all browsers support constructable
|
||
|
|
* `EventTarget`, so using a real `EventTarget` will error.
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
class EventTargetShim {
|
||
|
|
/**
|
||
|
|
* Creates an event listener registry
|
||
|
|
*
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
constructor() {
|
||
|
|
// A registry of event types to listeners.
|
||
|
|
this._eventListenerRegistry = {};
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
* @param {string} type
|
||
|
|
* @param {Function} listener
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
addEventListener(type, listener) {
|
||
|
|
this._getEventListenersByType(type).add(listener);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @param {string} type
|
||
|
|
* @param {Function} listener
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
removeEventListener(type, listener) {
|
||
|
|
this._getEventListenersByType(type).delete(listener);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @param {Event} event
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
dispatchEvent(event) {
|
||
|
|
event.target = this;
|
||
|
|
this._getEventListenersByType(event.type).forEach(
|
||
|
|
(listener) => listener(event));
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns a Set of listeners associated with the passed event type.
|
||
|
|
* If no handlers have been registered, an empty Set is returned.
|
||
|
|
*
|
||
|
|
* @param {string} type The event type.
|
||
|
|
* @return {Set} An array of handler functions.
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
_getEventListenersByType(type) {
|
||
|
|
return this._eventListenerRegistry[type] =
|
||
|
|
(this._eventListenerRegistry[type] || new Set());
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
export {EventTargetShim};
|