6 module.exports = Emitter;
9 * Initialize a new `Emitter`.
14 function Emitter(obj) {
15 if (obj) return mixin(obj);
19 * Mixin the emitter properties.
27 for (var key in Emitter.prototype) {
28 obj[key] = Emitter.prototype[key];
34 * Listen on the given `event` with `fn`.
36 * @param {String} event
37 * @param {Function} fn
42 Emitter.prototype.on = function(event, fn){
43 this._callbacks = this._callbacks || {};
44 (this._callbacks[event] = this._callbacks[event] || [])
50 * Adds an `event` listener that will be invoked a single
51 * time then automatically removed.
53 * @param {String} event
54 * @param {Function} fn
59 Emitter.prototype.once = function(event, fn){
61 this._callbacks = this._callbacks || {};
65 fn.apply(this, arguments);
74 * Remove the given callback for `event` or all
75 * registered callbacks.
77 * @param {String} event
78 * @param {Function} fn
83 Emitter.prototype.off = function(event, fn){
84 this._callbacks = this._callbacks || {};
85 var callbacks = this._callbacks[event];
86 if (!callbacks) return this;
88 // remove all handlers
89 if (1 == arguments.length) {
90 delete this._callbacks[event];
94 // remove specific handler
95 var i = callbacks.indexOf(fn._off || fn);
96 if (~i) callbacks.splice(i, 1);
101 * Emit `event` with the given args.
103 * @param {String} event
108 Emitter.prototype.emit = function(event){
109 this._callbacks = this._callbacks || {};
110 var args = [].slice.call(arguments, 1)
111 , callbacks = this._callbacks[event];
114 callbacks = callbacks.slice(0);
115 for (var i = 0, len = callbacks.length; i < len; ++i) {
116 callbacks[i].apply(this, args);
124 * Return array of callbacks for `event`.
126 * @param {String} event
131 Emitter.prototype.listeners = function(event){
132 this._callbacks = this._callbacks || {};
133 return this._callbacks[event] || [];
137 * Check if this emitter has `event` handlers.
139 * @param {String} event
144 Emitter.prototype.hasListeners = function(event){
145 return !! this.listeners(event).length;