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/*
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};