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