Javascript的觀察者模式

let event = {};
event.list = [];//增加訂閱者event.listen = function(fn){
 event.list.push(fn);
}//發(fā)布消息event.trigger = function(){ for(var i = 0,fn; fn = this.list[i++];) {
 fn.apply(this,arguments); 
 }
}let click = function(){ console.log('event：click');
}let hover = function(){ console.log('event：hover');
}
event.listen(click);
event.listen(hover);
event.trigger();//打印：‘event：click’'event：hover'

let Event = (function(){ var list = {},
 listen,
 trigger,
 remove;
 listen = function(key,fn){ list[key] = list[key]||[]; list[key].push(fn);
 };
 trigger = function(){ var key = Array.prototype.shift.call(arguments),
 fns = list[key]; if(!fns || fns.length === 0) { return false;
 } for(var i = 0, fn; fn = fns[i++];) {
 fn.apply(this,arguments);
 }
 };
 remove = function(key,fn){ var fns = list[key]; if(!fns) { return false;
 } if(!fn) {
 fns && (fns.length = 0);
 }else { for(var i = fns.length - 1; i >= 0; i--){ var _fn = fns[i]; if(_fn === fn) {
 fns.splice(i,1);
 }
 }
 }
 }; return {
 listen: listen,
 trigger: trigger,
 remove: remove
 }
})();
Event.listen('click', function(type) {
 console.log('event: ' + type +' click'); 
});
Event.trigger('click' , 'button');//打印'event: button click'