event_emitter.js

"use strict";
/**@type {any}*/
var EventEmitter = {};
var stopPropagation = function() { this.propagationStopped = true; };
var preventDefault = function() { this.defaultPrevented = true; };

EventEmitter._emit =
EventEmitter._dispatchEvent = function(eventName, e) {
    this._eventRegistry || (this._eventRegistry = {});
    this._defaultHandlers || (this._defaultHandlers = {});

    var listeners = this._eventRegistry[eventName] || [];
    var defaultHandler = this._defaultHandlers[eventName];
    if (!listeners.length && !defaultHandler)
        return;

    if (typeof e != "object" || !e)
        e = {};

    if (!e.type)
        e.type = eventName;
    if (!e.stopPropagation)
        e.stopPropagation = stopPropagation;
    if (!e.preventDefault)
        e.preventDefault = preventDefault;

    listeners = listeners.slice();
    for (var i=0; i<listeners.length; i++) {
        listeners[i](e, this);
        if (e.propagationStopped)
            break;
    }
    
    if (defaultHandler && !e.defaultPrevented)
        return defaultHandler(e, this);
};


EventEmitter._signal = function(eventName, e) {
    var listeners = (this._eventRegistry || {})[eventName];
    if (!listeners)
        return;
    listeners = listeners.slice();
    for (var i=0; i<listeners.length; i++)
        listeners[i](e, this);
};

EventEmitter.once = function(eventName, callback) {
    var _self = this;
    this.on(eventName, function newCallback() {
        _self.off(eventName, newCallback);
        callback.apply(null, arguments);
    });
    if (!callback) {
        /*global Promise*/
        return new Promise(function(resolve) {
            callback = resolve;
        });
    }
};


EventEmitter.setDefaultHandler = function(eventName, callback) {
    /**@type {any}*/
    var handlers = this._defaultHandlers;
    if (!handlers)
        handlers = this._defaultHandlers = {_disabled_: {}};
    
    if (handlers[eventName]) {
        var old = handlers[eventName];
        var disabled = handlers._disabled_[eventName];
        if (!disabled)
            handlers._disabled_[eventName] = disabled = [];
        disabled.push(old);
        var i = disabled.indexOf(callback);
        if (i != -1) 
            disabled.splice(i, 1);
    }
    handlers[eventName] = callback;
};
EventEmitter.removeDefaultHandler = function(eventName, callback) {
    var handlers = this._defaultHandlers;
    if (!handlers)
        return;
    var disabled = handlers._disabled_[eventName];
    
    if (handlers[eventName] == callback) {
        if (disabled)
            this.setDefaultHandler(eventName, disabled.pop());
    } else if (disabled) {
        var i = disabled.indexOf(callback);
        if (i != -1)
            disabled.splice(i, 1);
    }
};

EventEmitter.on =
EventEmitter.addEventListener = function(eventName, callback, capturing) {
    this._eventRegistry = this._eventRegistry || {};

    var listeners = this._eventRegistry[eventName];
    if (!listeners)
        listeners = this._eventRegistry[eventName] = [];

    if (listeners.indexOf(callback) == -1)
        listeners[capturing ? "unshift" : "push"](callback);
    return callback;
};

EventEmitter.off =
EventEmitter.removeListener =
EventEmitter.removeEventListener = function(eventName, callback) {
    this._eventRegistry = this._eventRegistry || {};

    var listeners = this._eventRegistry[eventName];
    if (!listeners)
        return;

    var index = listeners.indexOf(callback);
    if (index !== -1)
        listeners.splice(index, 1);
};
/**
 * @this {EventEmitter}
 */
EventEmitter.removeAllListeners = function(eventName) {
    if (!eventName) this._eventRegistry = this._defaultHandlers = undefined;
    if (this._eventRegistry) this._eventRegistry[eventName] = undefined;
    if (this._defaultHandlers) this._defaultHandlers[eventName] = undefined;
};

exports.EventEmitter = EventEmitter;