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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+'use strict';
+
+module.metadata = {
+ "stability": "stable"
+};
+
+const { on, once, off, setListeners } = require('./core');
+const { method, chainable } = require('../lang/functional/core');
+const { Class } = require('../core/heritage');
+
+/**
+ * `EventTarget` is an exemplar for creating an objects that can be used to
+ * add / remove event listeners on them. Events on these objects may be emitted
+ * via `emit` function exported by 'event/core' module.
+ */
+const EventTarget = Class({
+ /**
+ * Method initializes `this` event source. It goes through properties of a
+ * given `options` and registers listeners for the ones that look like an
+ * event listeners.
+ */
+ /**
+ * Method initializes `this` event source. It goes through properties of a
+ * given `options` and registers listeners for the ones that look like an
+ * event listeners.
+ */
+ initialize: function initialize(options) {
+ setListeners(this, options);
+ },
+ /**
+ * Registers an event `listener` that is called every time events of
+ * specified `type` are emitted.
+ * @param {String} type
+ * The type of event.
+ * @param {Function} listener
+ * The listener function that processes the event.
+ * @example
+ * worker.on('message', function (data) {
+ * console.log('data received: ' + data)
+ * })
+ */
+ on: chainable(method(on)),
+ /**
+ * Registers an event `listener` that is called once the next time an event
+ * of the specified `type` is emitted.
+ * @param {String} type
+ * The type of the event.
+ * @param {Function} listener
+ * The listener function that processes the event.
+ */
+ once: chainable(method(once)),
+ /**
+ * Removes an event `listener` for the given event `type`.
+ * @param {String} type
+ * The type of event.
+ * @param {Function} listener
+ * The listener function that processes the event.
+ */
+ removeListener: function removeListener(type, listener) {
+ // Note: We can't just wrap `off` in `method` as we do it for other methods
+ // cause skipping a second or third argument will behave very differently
+ // than intended. This way we make sure all arguments are passed and only
+ // one listener is removed at most.
+ off(this, type, listener);
+ return this;
+ },
+ // but we can wrap `off` here, as the semantics are the same
+ off: chainable(method(off))
+
+});
+exports.EventTarget = EventTarget;