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/**
* Expose `Emitter`.
*/
module.exports = Emitter;
/**
* Initialize a new `Emitter`.
*
* @api public
*/
function Emitter(obj) {
if (obj) return mixin(obj);
};
/**
* Mixin the emitter properties.
*
* @param {Object} obj
* @return {Object}
* @api private
*/
function mixin(obj) {
for (var key in Emitter.prototype) {
obj[key] = Emitter.prototype[key];
}
return obj;
}
/**
* Listen on the given `event` with `fn`.
*
* @param {String} event
* @param {Function} fn
* @return {Emitter}
* @api public
*/
Emitter.prototype.on = function(event, fn){
this._callbacks = this._callbacks || {};
(this._callbacks[event] = this._callbacks[event] || [])
.push(fn);
return this;
};
/**
* Adds an `event` listener that will be invoked a single
* time then automatically removed.
*
* @param {String} event
* @param {Function} fn
* @return {Emitter}
* @api public
*/
Emitter.prototype.once = function(event, fn){
var self = this;
this._callbacks = this._callbacks || {};
function on() {
self.off(event, on);
fn.apply(this, arguments);
}
fn._off = on;
this.on(event, on);
return this;
};
/**
* Remove the given callback for `event` or all
* registered callbacks.
*
* @param {String} event
* @param {Function} fn
* @return {Emitter}
* @api public
*/
Emitter.prototype.off = function(event, fn){
this._callbacks = this._callbacks || {};
var callbacks = this._callbacks[event];
if (!callbacks) return this;
// remove all handlers
if (1 == arguments.length) {
delete this._callbacks[event];
return this;
}
// remove specific handler
var i = callbacks.indexOf(fn._off || fn);
if (~i) callbacks.splice(i, 1);
return this;
};
/**
* Emit `event` with the given args.
*
* @param {String} event
* @param {Mixed} ...
* @return {Emitter}
*/
Emitter.prototype.emit = function(event){
this._callbacks = this._callbacks || {};
var args = [].slice.call(arguments, 1)
, callbacks = this._callbacks[event];
if (callbacks) {
callbacks = callbacks.slice(0);
for (var i = 0, len = callbacks.length; i < len; ++i) {
callbacks[i].apply(this, args);
}
}
return this;
};
/**
* Return array of callbacks for `event`.
*
* @param {String} event
* @return {Array}
* @api public
*/
Emitter.prototype.listeners = function(event){
this._callbacks = this._callbacks || {};
return this._callbacks[event] || [];
};
/**
* Check if this emitter has `event` handlers.
*
* @param {String} event
* @return {Boolean}
* @api public
*/
Emitter.prototype.hasListeners = function(event){
return !! this.listeners(event).length;
};
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