77 lines
2.0 KiB
JavaScript
77 lines
2.0 KiB
JavaScript
"use strict";
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module.exports = EventEmitter;
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/**
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* Constructs a new event emitter instance.
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* @classdesc A minimal event emitter.
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* @memberof util
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* @constructor
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*/
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function EventEmitter() {
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/**
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* Registered listeners.
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* @type {Object.<string,*>}
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* @private
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*/
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this._listeners = {};
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}
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/**
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* Registers an event listener.
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* @param {string} evt Event name
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* @param {function} fn Listener
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* @param {*} [ctx] Listener context
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* @returns {util.EventEmitter} `this`
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*/
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EventEmitter.prototype.on = function on(evt, fn, ctx) {
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(this._listeners[evt] || (this._listeners[evt] = [])).push({
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fn : fn,
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ctx : ctx || this
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});
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return this;
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};
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/**
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* Removes an event listener or any matching listeners if arguments are omitted.
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* @param {string} [evt] Event name. Removes all listeners if omitted.
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* @param {function} [fn] Listener to remove. Removes all listeners of `evt` if omitted.
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* @returns {util.EventEmitter} `this`
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*/
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EventEmitter.prototype.off = function off(evt, fn) {
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if (evt === undefined)
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this._listeners = {};
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else {
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if (fn === undefined)
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this._listeners[evt] = [];
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else {
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var listeners = this._listeners[evt];
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for (var i = 0; i < listeners.length;)
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if (listeners[i].fn === fn)
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listeners.splice(i, 1);
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else
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++i;
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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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* Emits an event by calling its listeners with the specified arguments.
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* @param {string} evt Event name
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* @param {...*} args Arguments
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* @returns {util.EventEmitter} `this`
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*/
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EventEmitter.prototype.emit = function emit(evt) {
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var listeners = this._listeners[evt];
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if (listeners) {
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var args = [],
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i = 1;
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for (; i < arguments.length;)
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args.push(arguments[i++]);
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for (i = 0; i < listeners.length;)
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listeners[i].fn.apply(listeners[i++].ctx, args);
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}
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return this;
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};
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