张静宜对订阅-发布模式的理解

var Event = (function(){
 var global = this,
 Event,
 _default = ‘default‘;
 Event = function(){
 var _listen,
 _trigger,
 _remove,
 _slice = Array.prototype.slice,
 _shift = Array.prototype.shift,
 _unshift = Array.prototype.unshift,
 namespaceCache = {},
 _create,
 find,
 each = function( ary, fn ){
 var ret;
 for ( var i = 0, l = ary.length; i < l; i++ ){ 
var n = ary[i];
 ret = fn.call( n, i, n);
 }
 return ret;
 };
 _listen = function( key, fn, cache ){
 if ( !cache[ key ] ){
 cache[ key ] = [];
 }
 cache[key].push( fn );
 };
 _remove = function( key, cache ,fn){
 if ( cache[ key ] ){
 if( fn ){
 for( var i = cache[ key ].length; i >= 0; i-- ){
 if( cache[ key ][i] === fn ){
 cache[ key ].splice( i, 1 );
 }
 }
 }else{
 cache[ key ] = [];
 }
 }
 };
 _trigger = function(){
 var cache = _shift.call(arguments),
 key = _shift.call(arguments),
 args = arguments,
 _self = this,
 ret,
 stack = cache[ key ];
 if ( !stack || !stack.length ){
 return;
 }
 return each( stack, function(){
 return this.apply( _self, args );
 });
 };
 _create = function( namespace ){
 var namespace = namespace || _default;
 var cache = {},
 offlineStack = [], // 离线事件
 ret = {
 listen: function( key, fn, last ){
 _listen( key, fn, cache );
 if ( offlineStack === null ){
 return;
 }
 if ( last === ‘last‘ ){ 
offlineStack.length && offlineStack.pop()();
 }else{
 each( offlineStack, function(){
 this();
 });
 }
 offlineStack = null;
 },
 one: function( key, fn, last ){
 _remove( key, cache );
 this.listen( key, fn ,last );
 },
 remove: function( key, fn ){
 _remove( key, cache ,fn);
 },
 trigger: function(){
 var fn,
 args,
 _self = this;
 _unshift.call( arguments, cache );
 args = arguments;
 fn = function(){
 return _trigger.apply( _self, args );
 };
 if ( offlineStack ){
 return offlineStack.push( fn );
 }
 return fn();
 }
 };
 return namespace ?
 ( namespaceCache[ namespace ] ? namespaceCache[ namespace ] :
 namespaceCache[ namespace ] = ret )
 : ret;
 };
 return {
 create: _create,
 one: function( key,fn, last ){
 var event = this.create( );
 event.one( key,fn,last );
 },
 remove: function( key,fn ){
 var event = this.create( );
 event.remove( key,fn );
 },
 listen: function( key, fn, last ){
 var event = this.create( );
 event.listen( key, fn, last );
 },
 trigger: function(){ 
var event = this.create( );
 event.trigger.apply( this, arguments );
 }
 };
 }();
 return Event;
})();