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61 lines
1.7 KiB
61 lines
1.7 KiB
2 years ago
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/*
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Copyright 2019 Google LLC
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Use of this source code is governed by an MIT-style
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license that can be found in the LICENSE file or at
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https://opensource.org/licenses/MIT.
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*/
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/**
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* A minimal `EventTarget` shim.
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* This is necessary because not all browsers support constructable
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* `EventTarget`, so using a real `EventTarget` will error.
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* @private
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*/
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export class WorkboxEventTarget {
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constructor() {
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this._eventListenerRegistry = new Map();
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}
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/**
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* @param {string} type
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* @param {Function} listener
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* @private
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*/
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addEventListener(type, listener) {
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const foo = this._getEventListenersByType(type);
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foo.add(listener);
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}
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/**
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* @param {string} type
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* @param {Function} listener
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* @private
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*/
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removeEventListener(type, listener) {
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this._getEventListenersByType(type).delete(listener);
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}
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/**
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* @param {Object} event
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* @private
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*/
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dispatchEvent(event) {
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event.target = this;
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const listeners = this._getEventListenersByType(event.type);
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for (const listener of listeners) {
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listener(event);
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}
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}
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/**
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* Returns a Set of listeners associated with the passed event type.
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* If no handlers have been registered, an empty Set is returned.
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*
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* @param {string} type The event type.
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* @return {Set<ListenerCallback>} An array of handler functions.
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* @private
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*/
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_getEventListenersByType(type) {
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if (!this._eventListenerRegistry.has(type)) {
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this._eventListenerRegistry.set(type, new Set());
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}
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return this._eventListenerRegistry.get(type);
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}
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}
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