//实现一个发布订阅模块，subscribe，unsubscribe，publish接口分别用来实现订阅，取消订阅，和发布事件的功能
//代码尽可能设计考虑更多的边界条件
class Pubsub {
        constructor(){
            this.events = {}
        }

    subscribe(event,action){
            if(!event||!action){
                return;
                //参数为空这个当时也没写
            }
            //这里我原来只写的是 this.events[event],但这样确实可能会访问到原型上的方法，不妥
            if(!this.events.hasOwnProperty(event)){
                this.events[event] = [action]
                return
            }
            this.events[event].push(action)
             return action
    }
    unsubscribe(event,action){
            if(!event&&!action){
                this.events = {}
                return
            }
            if(!action) {
                this.events[event] = []
                return
            }
            // if(!action.name){  这个部分是hr后提的额外需求，取消匿名函数，但我这个方法可能定是错的，正确方法见下：
            //     //通过action.name判断是否为匿名函数，匿名函数的话就通过将其转化为字符串进行比较
            //     this.events[event] =  this.events[event].filter(fn=>fn.toString().trim()!==action.toString().trim())
            //     return
            // }
            this.events[event] =  this.events[event].filter(fn=>fn!==action)

        }
    publish(event){
          if(this.events.hasOwnProperty(event)) {
              this.events[event].forEach(fn=>fn())
          }
    }
}
let ob = new Pubsub();

ob.subscribe('add', (val) => console.log(123));
ob.subscribe('add', (val) => console.log(123));
// ob.unsubscribe('add',(val) => console.log(123))
//正确方法，给subscribe添加返回值，为函数应用
let temp  = ob.subscribe('add', (val) => console.log(123));

ob.unsubscribe('add',temp)

ob.publish('add');

//结果，123,123