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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;
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