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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": "deprecated"
};
const ERROR_TYPE = 'error',
UNCAUGHT_ERROR = 'An error event was dispatched for which there was'
+ ' no listener.',
BAD_LISTENER = 'The event listener must be a function.';
/**
* This object is used to create an `EventEmitter` that, useful for composing
* objects that emit events. It implements an interface like `EventTarget` from
* DOM Level 2, which is implemented by Node objects in implementations that
* support the DOM Event Model.
* @see http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-EventTarget
* @see http://nodejs.org/api.html#EventEmitter
* @see http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/events/EventDispatcher.html
*/
const eventEmitter = {
/**
* 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: function on(type, listener) {
if ('function' !== typeof listener)
throw new Error(BAD_LISTENER);
let listeners = this._listeners(type);
if (0 > listeners.indexOf(listener))
listeners.push(listener);
// Use of `_public` is required by the legacy traits code that will go away
// once bug-637633 is fixed.
return this._public || this;
},
/**
* 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: function once(type, listener) {
this.on(type, function selfRemovableListener() {
this.removeListener(type, selfRemovableListener);
listener.apply(this, arguments);
});
},
/**
* Unregister `listener` for the specified event type.
* @param {String} type
* The type of event.
* @param {Function} listener
* The listener function that processes the event.
*/
removeListener: function removeListener(type, listener) {
if ('function' !== typeof listener)
throw new Error(BAD_LISTENER);
let listeners = this._listeners(type),
index = listeners.indexOf(listener);
if (0 <= index)
listeners.splice(index, 1);
// Use of `_public` is required by the legacy traits code, that will go away
// once bug-637633 is fixed.
return this._public || this;
},
/**
* Hash of listeners on this EventEmitter.
*/
_events: null,
/**
* Returns an array of listeners for the specified event `type`. This array
* can be manipulated, e.g. to remove listeners.
* @param {String} type
* The type of event.
*/
_listeners: function listeners(type) {
let events = this._events || (this._events = {});
return events[type] || (events[type] = []);
},
/**
* Execute each of the listeners in order with the supplied arguments.
* Returns `true` if listener for this event was called, `false` if there are
* no listeners for this event `type`.
*
* All the exceptions that are thrown by listeners during the emit
* are caught and can be handled by listeners of 'error' event. Thrown
* exceptions are passed as an argument to an 'error' event listener.
* If no 'error' listener is registered exception will propagate to a
* caller of this method.
*
* **It's recommended to have a default 'error' listener in all the complete
* composition that in worst case may dump errors to the console.**
*
* @param {String} type
* The type of event.
* @params {Object|Number|String|Boolean}
* Arguments that will be passed to listeners.
* @returns {Boolean}
*/
_emit: function _emit(type, event) {
let args = Array.slice(arguments);
// Use of `_public` is required by the legacy traits code that will go away
// once bug-637633 is fixed.
args.unshift(this._public || this);
return this._emitOnObject.apply(this, args);
},
/**
* A version of _emit that lets you specify the object on which listeners are
* called. This is a hack that is sometimes necessary when such an object
* (exports, for example) cannot be an EventEmitter for some reason, but other
* object(s) managing events for the object are EventEmitters. Once bug
* 577782 is fixed, this method shouldn't be necessary.
*
* @param {object} targetObj
* The object on which listeners will be called.
* @param {string} type
* The event name.
* @param {value} event
* The first argument to pass to listeners.
* @param {value} ...
* More arguments to pass to listeners.
* @returns {boolean}
*/
_emitOnObject: function _emitOnObject(targetObj, type, event /* , ... */) {
let listeners = this._listeners(type).slice(0);
// If there is no 'error' event listener then throw.
if (type === ERROR_TYPE && !listeners.length)
console.exception(event);
if (!listeners.length)
return false;
let params = Array.slice(arguments, 2);
for each (let listener in listeners) {
try {
listener.apply(targetObj, params);
} catch(e) {
// Bug 726967: Ignore exceptions being throws while notifying the error
// in order to avoid infinite loops.
if (type !== ERROR_TYPE)
this._emit(ERROR_TYPE, e);
else
console.exception("Exception in error event listener " + e);
}
}
return true;
},
/**
* Removes all the event listeners for the specified event `type`.
* @param {String} type
* The type of event.
*/
_removeAllListeners: function _removeAllListeners(type) {
if (typeof type == "undefined") {
this._events = null;
return this;
}
this._listeners(type).splice(0);
return this;
}
};
exports.EventEmitter = require("./traits").Trait.compose(eventEmitter);
exports.EventEmitterTrait = require('./light-traits').Trait(eventEmitter);
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