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'use strict';
var has = Object.prototype.hasOwnProperty;
//
// We store our EE objects in a plain object whose properties are event names.
// If `Object.create(null)` is not supported we prefix the event names with a
// `~` to make sure that the built-in object properties are not overridden or
// used as an attack vector.
// We also assume that `Object.create(null)` is available when the event name
// is an ES6 Symbol.
//
var prefix = typeof Object.create !== 'function' ? '~' : false;
/**
* Representation of a single EventEmitter function.
*
* @param {Function} fn Event handler to be called.
* @param {Mixed} context Context for function execution.
* @param {Boolean} [once=false] Only emit once
* @api private
*/
function EE(fn, context, once) {
this.fn = fn;
this.context = context;
this.once = once || false;
}
/**
* Minimal EventEmitter interface that is molded against the Node.js
* EventEmitter interface.
*
* @constructor
* @api public
*/
function EventEmitter() { /* Nothing to set */ }
/**
* Hold the assigned EventEmitters by name.
*
* @type {Object}
* @private
*/
EventEmitter.prototype._events = undefined;
/**
* Return an array listing the events for which the emitter has registered
* listeners.
*
* @returns {Array}
* @api public
*/
EventEmitter.prototype.eventNames = function eventNames() {
var events = this._events
, names = []
, name;
if (!events) return names;
for (name in 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 a list of assigned event listeners.
*
* @param {String} event The events that should be listed.
* @param {Boolean} exists We only need to know if there are listeners.
* @returns {Array|Boolean}
* @api public
*/
EventEmitter.prototype.listeners = function listeners(event, exists) {
var evt = prefix ? prefix + event : event
, available = this._events && this._events[evt];
if (exists) return !!available;
if (!available) return [];
if (available.fn) return [available.fn];
for (var i = 0, l = available.length, ee = new Array(l); i < l; i++) {
ee[i] = available[i].fn;
}
return ee;
};
/**
* Emit an event to all registered event listeners.
*
* @param {String} event The name of the event.
* @returns {Boolean} Indication if we've emitted an event.
* @api public
*/
EventEmitter.prototype.emit = function emit(event, a1, a2, a3, a4, a5) {
var evt = prefix ? prefix + event : event;
if (!this._events || !this._events[evt]) return false;
var listeners = this._events[evt]
, len = arguments.length
, args
, i;
if ('function' === typeof 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;
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;
};
/**
* Register a new EventListener for the given event.
*
* @param {String} event Name of the event.
* @param {Function} fn Callback function.
* @param {Mixed} [context=this] The context of the function.
* @api public
*/
EventEmitter.prototype.on = function on(event, fn, context) {
var listener = new EE(fn, context || this)
, evt = prefix ? prefix + event : event;
if (!this._events) this._events = prefix ? {} : Object.create(null);
if (!this._events[evt]) this._events[evt] = listener;
else {
if (!this._events[evt].fn) this._events[evt].push(listener);
else this._events[evt] = [
this._events[evt], listener
];
}
return this;
};
/**
* Add an EventListener that's only called once.
*
* @param {String} event Name of the event.
* @param {Function} fn Callback function.
* @param {Mixed} [context=this] The context of the function.
* @api public
*/
EventEmitter.prototype.once = function once(event, fn, context) {
var listener = new EE(fn, context || this, true)
, evt = prefix ? prefix + event : event;
if (!this._events) this._events = prefix ? {} : Object.create(null);
if (!this._events[evt]) this._events[evt] = listener;
else {
if (!this._events[evt].fn) this._events[evt].push(listener);
else this._events[evt] = [
this._events[evt], listener
];
}
return this;
};
/**
* Remove event listeners.
*
* @param {String} event The event we want to remove.
* @param {Function} fn The listener that we need to find.
* @param {Mixed} context Only remove listeners matching this context.
* @param {Boolean} once Only remove once listeners.
* @api public
*/
EventEmitter.prototype.removeListener = function removeListener(event, fn, context, once) {
var evt = prefix ? prefix + event : event;
if (!this._events || !this._events[evt]) return this;
var listeners = this._events[evt]
, events = [];
if (fn) {
if (listeners.fn) {
if (
listeners.fn !== fn
|| (once && !listeners.once)
|| (context && listeners.context !== context)
) {
events.push(listeners);
}
} else {
for (var i = 0, 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 {
delete this._events[evt];
}
return this;
};
/**
* Remove all listeners or only the listeners for the specified event.
*
* @param {String} event The event want to remove all listeners for.
* @api public
*/
EventEmitter.prototype.removeAllListeners = function removeAllListeners(event) {
if (!this._events) return this;
if (event) delete this._events[prefix ? prefix + event : event];
else this._events = prefix ? {} : Object.create(null);
return this;
};
//
// Alias methods names because people roll like that.
//
EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
EventEmitter.prototype.addListener = EventEmitter.prototype.on;
//
// This function doesn't apply anymore.
//
EventEmitter.prototype.setMaxListeners = function setMaxListeners() {
return this;
};
//
// Expose the prefix.
//
EventEmitter.prefixed = prefix;
//
// Expose the module.
//
if ('undefined' !== typeof module) {
module.exports = EventEmitter;
}