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'use strict';
var has = Object.prototype.hasOwnProperty
, prefix = '~';
/**
* Constructor to create a storage for our `EE` objects.
* An `Events` instance is a plain object whose properties are event names.
*
* @constructor
* @private
*/
function Events() {}
//
// We try to not inherit from `Object.prototype`. In some engines creating an
// instance in this way is faster than calling `Object.create(null)` directly.
// If `Object.create(null)` is not supported we prefix the event names with a
// character to make sure that the built-in object properties are not
// overridden or used as an attack vector.
//
if (Object.create) {
Events.prototype = Object.create(null);
//
// This hack is needed because the `__proto__` property is still inherited in
// some old browsers like Android 4, iPhone 5.1, Opera 11 and Safari 5.
//
if (!new Events().__proto__) prefix = false;
}
/**
* Representation of a single event listener.
*
* @param {Function} fn The listener function.
* @param {*} context The context to invoke the listener with.
* @param {Boolean} [once=false] Specify if the listener is a one-time listener.
* @constructor
* @private
*/
function EE(fn, context, once) {
this.fn = fn;
this.context = context;
this.once = once || false;
}
/**
* Add a listener for a given event.
*
* @param {EventEmitter} emitter Reference to the `EventEmitter` instance.
* @param {(String|Symbol)} event The event name.
* @param {Function} fn The listener function.
* @param {*} context The context to invoke the listener with.
* @param {Boolean} once Specify if the listener is a one-time listener.
* @returns {EventEmitter}
* @private
*/
function addListener(emitter, event, fn, context, once) {
if (typeof fn !== 'function') {
throw new TypeError('The listener must be a function');
}
var listener = new EE(fn, context || emitter, once)
, evt = prefix ? prefix + event : event;
if (!emitter._events[evt]) emitter._events[evt] = listener, emitter._eventsCount++;
else if (!emitter._events[evt].fn) emitter._events[evt].push(listener);
else emitter._events[evt] = [emitter._events[evt], listener];
return emitter;
}
/**
* Clear event by name.
*
* @param {EventEmitter} emitter Reference to the `EventEmitter` instance.
* @param {(String|Symbol)} evt The Event name.
* @private
*/
function clearEvent(emitter, evt) {
if (--emitter._eventsCount === 0) emitter._events = new Events();
else delete emitter._events[evt];
}
/**
* Minimal `EventEmitter` interface that is molded against the Node.js
* `EventEmitter` interface.
*
* @constructor
* @public
*/
function EventEmitter() {
this._events = new Events();
this._eventsCount = 0;
}
/**
* Return an array listing the events for which the emitter has registered
* listeners.
*
* @returns {Array}
* @public
*/
EventEmitter.prototype.eventNames = function eventNames() {
var names = []
, events
, name;
if (this._eventsCount === 0) return names;
for (name in (events = this._events)) {
if (has.call(events, name)) names.push(prefix ? name.slice(1) : name);
}
if (Object.getOwnPropertySymbols) {
return names.concat(Object.getOwnPropertySymbols(events));
}
return names;
};
/**
* Return the listeners registered for a given event.
*
* @param {(String|Symbol)} event The event name.
* @returns {Array} The registered listeners.
* @public
*/
EventEmitter.prototype.listeners = function listeners(event) {
var evt = prefix ? prefix + event : event
, handlers = this._events[evt];
if (!handlers) return [];
if (handlers.fn) return [handlers.fn];
for (var i = 0, l = handlers.length, ee = new Array(l); i < l; i++) {
ee[i] = handlers[i].fn;
}
return ee;
};
/**
* Return the number of listeners listening to a given event.
*
* @param {(String|Symbol)} event The event name.
* @returns {Number} The number of listeners.
* @public
*/
EventEmitter.prototype.listenerCount = function listenerCount(event) {
var evt = prefix ? prefix + event : event
, listeners = this._events[evt];
if (!listeners) return 0;
if (listeners.fn) return 1;
return listeners.length;
};
/**
* Calls each of the listeners registered for a given event.
*
* @param {(String|Symbol)} event The event name.
* @returns {Boolean} `true` if the event had listeners, else `false`.
* @public
*/
EventEmitter.prototype.emit = function emit(event, a1, a2, a3, a4, a5) {
var evt = prefix ? prefix + event : event;
if (!this._events[evt]) return false;
var listeners = this._events[evt]
, len = arguments.length
, args
, i;
if (listeners.fn) {
if (listeners.once) this.removeListener(event, listeners.fn, undefined, true);
switch (len) {
case 1: return listeners.fn.call(listeners.context), true;
case 2: return listeners.fn.call(listeners.context, a1), true;
case 3: return listeners.fn.call(listeners.context, a1, a2), true;
case 4: return listeners.fn.call(listeners.context, a1, a2, a3), true;
case 5: return listeners.fn.call(listeners.context, a1, a2, a3, a4), true;
case 6: return listeners.fn.call(listeners.context, a1, a2, a3, a4, a5), true;
}
for (i = 1, args = new Array(len -1); i < len; i++) {
args[i - 1] = arguments[i];
}
listeners.fn.apply(listeners.context, args);
} else {
var length = listeners.length
, j;
for (i = 0; i < length; i++) {
if (listeners[i].once) this.removeListener(event, listeners[i].fn, undefined, true);
switch (len) {
case 1: listeners[i].fn.call(listeners[i].context); break;
case 2: listeners[i].fn.call(listeners[i].context, a1); break;
case 3: listeners[i].fn.call(listeners[i].context, a1, a2); break;
case 4: listeners[i].fn.call(listeners[i].context, a1, a2, a3); break;
default:
if (!args) for (j = 1, args = new Array(len -1); j < len; j++) {
args[j - 1] = arguments[j];
}
listeners[i].fn.apply(listeners[i].context, args);
}
}
}
return true;
};
/**
* Add a listener for a given event.
*
* @param {(String|Symbol)} event The event name.
* @param {Function} fn The listener function.
* @param {*} [context=this] The context to invoke the listener with.
* @returns {EventEmitter} `this`.
* @public
*/
EventEmitter.prototype.on = function on(event, fn, context) {
return addListener(this, event, fn, context, false);
};
/**
* Add a one-time listener for a given event.
*
* @param {(String|Symbol)} event The event name.
* @param {Function} fn The listener function.
* @param {*} [context=this] The context to invoke the listener with.
* @returns {EventEmitter} `this`.
* @public
*/
EventEmitter.prototype.once = function once(event, fn, context) {
return addListener(this, event, fn, context, true);
};
/**
* Remove the listeners of a given event.
*
* @param {(String|Symbol)} event The event name.
* @param {Function} fn Only remove the listeners that match this function.
* @param {*} context Only remove the listeners that have this context.
* @param {Boolean} once Only remove one-time listeners.
* @returns {EventEmitter} `this`.
* @public
*/
EventEmitter.prototype.removeListener = function removeListener(event, fn, context, once) {
var evt = prefix ? prefix + event : event;
if (!this._events[evt]) return this;
if (!fn) {
clearEvent(this, evt);
return this;
}
var listeners = this._events[evt];
if (listeners.fn) {
if (
listeners.fn === fn &&
(!once || listeners.once) &&
(!context || listeners.context === context)
) {
clearEvent(this, evt);
}
} else {
for (var i = 0, events = [], length = listeners.length; i < length; i++) {
if (
listeners[i].fn !== fn ||
(once && !listeners[i].once) ||
(context && listeners[i].context !== context)
) {
events.push(listeners[i]);
}
}
//
// Reset the array, or remove it completely if we have no more listeners.
//
if (events.length) this._events[evt] = events.length === 1 ? events[0] : events;
else clearEvent(this, evt);
}
return this;
};
/**
* Remove all listeners, or those of the specified event.
*
* @param {(String|Symbol)} [event] The event name.
* @returns {EventEmitter} `this`.
* @public
*/
EventEmitter.prototype.removeAllListeners = function removeAllListeners(event) {
var evt;
if (event) {
evt = prefix ? prefix + event : event;
if (this._events[evt]) clearEvent(this, evt);
} else {
this._events = new Events();
this._eventsCount = 0;
}
return this;
};
//
// Alias methods names because people roll like that.
//
EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
EventEmitter.prototype.addListener = EventEmitter.prototype.on;
//
// Expose the prefix.
//
EventEmitter.prefixed = prefix;
//
// Allow `EventEmitter` to be imported as module namespace.
//
EventEmitter.EventEmitter = EventEmitter;
//
// Expose the module.
//
if ('undefined' !== typeof module) {
module.exports = EventEmitter;
}