观察者模式与改变 function

Question

我尝试做一个简单的观察者模式。 通知订户换餐。 但在执行时出现错误：TypeError: foodChanger.addEventListener is not a function

这是我的代码：

class EventObserver {
        constructor() {
          this.observers = [];
        }

        subscribe(fn) {
          this.observers.push(fn);
        }

        unsubscribe(fn) {
          this.observers = this.observers.filter((subscriber) => subscriber !== fn);
        }

        broadcast(data) {
          this.observers.forEach((subscriber) => subscriber(data));
        }
      }

      const food = 'fruit'

      const blogObserver = new EventObserver();

      blogObserver.subscribe(() => {
        food.uptade(this);
      });
      const foodChanger = function () {
        const foods = ['vegetable', 'pizza', 'salad'];
        const timeSpin =  setInterval(()=>{this.food = foods[Math.floor(Math.random()*foods.length)];    
        },200);
        setTimeout(() => {
            clearInterval(timeSpin)
            }, 2000);
    }


      foodChanger.addEventListener('keyup', () => blogObserver.broadcast(foodChanger));

Answer 1

您的foodChanger变量是 function，因此不是具有addEventListener方法的EventTarget 。