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290 lines
7.6 KiB
290 lines
7.6 KiB
6 years ago
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'use strict';
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var has = Object.prototype.hasOwnProperty;
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//
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// We store our EE objects in a plain object whose properties are event names.
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// If `Object.create(null)` is not supported we prefix the event names with a
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// `~` to make sure that the built-in object properties are not overridden or
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// used as an attack vector.
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// We also assume that `Object.create(null)` is available when the event name
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// is an ES6 Symbol.
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//
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var prefix = typeof Object.create !== 'function' ? '~' : false;
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/**
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* Representation of a single EventEmitter function.
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*
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* @param {Function} fn Event handler to be called.
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* @param {Mixed} context Context for function execution.
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* @param {Boolean} [once=false] Only emit once
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* @api 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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* 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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* @api public
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*/
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function EventEmitter() { /* Nothing to set */ }
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/**
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* Hold the assigned EventEmitters by name.
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*
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* @type {Object}
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* @private
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*/
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EventEmitter.prototype._events = undefined;
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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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* @api public
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*/
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EventEmitter.prototype.eventNames = function eventNames() {
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var events = this._events
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, names = []
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, name;
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if (!events) return names;
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for (name in 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 a list of assigned event listeners.
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*
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* @param {String} event The events that should be listed.
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* @param {Boolean} exists We only need to know if there are listeners.
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* @returns {Array|Boolean}
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* @api public
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*/
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EventEmitter.prototype.listeners = function listeners(event, exists) {
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var evt = prefix ? prefix + event : event
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, available = this._events && this._events[evt];
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if (exists) return !!available;
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if (!available) return [];
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if (available.fn) return [available.fn];
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for (var i = 0, l = available.length, ee = new Array(l); i < l; i++) {
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ee[i] = available[i].fn;
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}
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return ee;
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};
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/**
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* Emit an event to all registered event listeners.
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*
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* @param {String} event The name of the event.
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* @returns {Boolean} Indication if we've emitted an event.
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* @api 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 || !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 ('function' === typeof 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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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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* Register a new EventListener for the given event.
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*
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* @param {String} event Name of the event.
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* @param {Function} fn Callback function.
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* @param {Mixed} [context=this] The context of the function.
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* @api public
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*/
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EventEmitter.prototype.on = function on(event, fn, context) {
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var listener = new EE(fn, context || this)
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, evt = prefix ? prefix + event : event;
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if (!this._events) this._events = prefix ? {} : Object.create(null);
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if (!this._events[evt]) this._events[evt] = listener;
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else {
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if (!this._events[evt].fn) this._events[evt].push(listener);
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else this._events[evt] = [
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this._events[evt], listener
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];
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}
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return this;
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};
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/**
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* Add an EventListener that's only called once.
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*
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* @param {String} event Name of the event.
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* @param {Function} fn Callback function.
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* @param {Mixed} [context=this] The context of the function.
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* @api public
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*/
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EventEmitter.prototype.once = function once(event, fn, context) {
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var listener = new EE(fn, context || this, true)
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, evt = prefix ? prefix + event : event;
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if (!this._events) this._events = prefix ? {} : Object.create(null);
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if (!this._events[evt]) this._events[evt] = listener;
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else {
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if (!this._events[evt].fn) this._events[evt].push(listener);
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else this._events[evt] = [
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this._events[evt], listener
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];
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}
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return this;
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};
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/**
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* Remove event listeners.
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*
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* @param {String} event The event we want to remove.
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* @param {Function} fn The listener that we need to find.
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* @param {Mixed} context Only remove listeners matching this context.
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* @param {Boolean} once Only remove once listeners.
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* @api 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 || !this._events[evt]) return this;
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var listeners = this._events[evt]
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, events = [];
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if (fn) {
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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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events.push(listeners);
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}
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} else {
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for (var i = 0, 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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}
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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) {
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this._events[evt] = events.length === 1 ? events[0] : events;
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} else {
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delete this._events[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 only the listeners for the specified event.
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*
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* @param {String} event The event want to remove all listeners for.
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* @api public
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*/
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EventEmitter.prototype.removeAllListeners = function removeAllListeners(event) {
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if (!this._events) return this;
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if (event) delete this._events[prefix ? prefix + event : event];
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else this._events = prefix ? {} : Object.create(null);
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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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// This function doesn't apply anymore.
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//
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EventEmitter.prototype.setMaxListeners = function setMaxListeners() {
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return this;
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};
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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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// 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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