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