function Events(){

            var obj = {};

            this.on=function(key,fn){

               var stack;

               stack = obj[key] || (obj[key] =[]);

               return stack.push(fn);

            }

            this.off=function(key){

                var stack;

                return (stack=obj[key]) != null ? stack.length= : void ;//此处stack.length=0不等同于stack=[],如果设置stack=[],并不能作用于object[key]

            }

            this.once=function(key,fn){

                this.off(key);

                return this.on(key,fn);

            }

            this.trigger=function(){

                var key,stack,i;

                key = [].shift.call(arguments);

                stack = obj[key]||(obj[key] = []);

                for(i=;i<stack.length;i++){

                    stack[i].apply(this,arguments);

                }

            }

        }

        var events = new Events();

        events.on("play",function(data){

            console.log(data.name)

        });

        events.on("play",function(data){

            console.log(data.age)

        });

        events.trigger("play",{name:"dpd",age:})