gecko/toolkit/devtools/event-emitter.js
J. Ryan Stinnett ca83343b85 Bug 976679 - Move event-emitter to toolkit. r=paul
--HG--
rename : browser/devtools/shared/event-emitter.js => toolkit/devtools/event-emitter.js
rename : browser/devtools/shared/test/browser_eventemitter_basic.js => toolkit/devtools/tests/mochitest/test_eventemitter_basic.html
2014-02-25 22:22:05 -06:00

138 lines
4.3 KiB
JavaScript

/* 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/. */
/**
* EventEmitter.
*/
this.EventEmitter = function EventEmitter() {};
if (typeof(require) === "function") {
module.exports = EventEmitter;
var {Cu} = require("chrome");
} else {
var EXPORTED_SYMBOLS = ["EventEmitter"];
var Cu = this["Components"].utils;
}
const { Promise: promise } = Cu.import("resource://gre/modules/Promise.jsm", {});
/**
* Decorate an object with event emitter functionality.
*
* @param Object aObjectToDecorate
* Bind all public methods of EventEmitter to
* the aObjectToDecorate object.
*/
EventEmitter.decorate = function EventEmitter_decorate (aObjectToDecorate) {
let emitter = new EventEmitter();
aObjectToDecorate.on = emitter.on.bind(emitter);
aObjectToDecorate.off = emitter.off.bind(emitter);
aObjectToDecorate.once = emitter.once.bind(emitter);
aObjectToDecorate.emit = emitter.emit.bind(emitter);
};
EventEmitter.prototype = {
/**
* Connect a listener.
*
* @param string aEvent
* The event name to which we're connecting.
* @param function aListener
* Called when the event is fired.
*/
on: function EventEmitter_on(aEvent, aListener) {
if (!this._eventEmitterListeners)
this._eventEmitterListeners = new Map();
if (!this._eventEmitterListeners.has(aEvent)) {
this._eventEmitterListeners.set(aEvent, []);
}
this._eventEmitterListeners.get(aEvent).push(aListener);
},
/**
* Listen for the next time an event is fired.
*
* @param string aEvent
* The event name to which we're connecting.
* @param function aListener
* (Optional) Called when the event is fired. Will be called at most
* one time.
* @return promise
* A promise which is resolved when the event next happens. The
* resolution value of the promise is the first event argument. If
* you need access to second or subsequent event arguments (it's rare
* that this is needed) then use aListener
*/
once: function EventEmitter_once(aEvent, aListener) {
let deferred = promise.defer();
let handler = function(aEvent, aFirstArg) {
this.off(aEvent, handler);
if (aListener) {
aListener.apply(null, arguments);
}
deferred.resolve(aFirstArg);
}.bind(this);
handler._originalListener = aListener;
this.on(aEvent, handler);
return deferred.promise;
},
/**
* Remove a previously-registered event listener. Works for events
* registered with either on or once.
*
* @param string aEvent
* The event name whose listener we're disconnecting.
* @param function aListener
* The listener to remove.
*/
off: function EventEmitter_off(aEvent, aListener) {
if (!this._eventEmitterListeners)
return;
let listeners = this._eventEmitterListeners.get(aEvent);
if (listeners) {
this._eventEmitterListeners.set(aEvent, listeners.filter(l => {
return l !== aListener && l._originalListener !== aListener;
}));
}
},
/**
* Emit an event. All arguments to this method will
* be sent to listner functions.
*/
emit: function EventEmitter_emit(aEvent) {
if (!this._eventEmitterListeners || !this._eventEmitterListeners.has(aEvent))
return;
let originalListeners = this._eventEmitterListeners.get(aEvent);
for (let listener of this._eventEmitterListeners.get(aEvent)) {
// If the object was destroyed during event emission, stop
// emitting.
if (!this._eventEmitterListeners) {
break;
}
// If listeners were removed during emission, make sure the
// event handler we're going to fire wasn't removed.
if (originalListeners === this._eventEmitterListeners.get(aEvent) ||
this._eventEmitterListeners.get(aEvent).some(function(l) l === listener)) {
try {
listener.apply(null, arguments);
}
catch (ex) {
// Prevent a bad listener from interfering with the others.
let msg = ex + ": " + ex.stack;
Cu.reportError(msg);
dump(msg + "\n");
}
}
}
}
};