class Producer {

    constructor() {

        this.listeners = [];

    }

    addListener(listener) {

        if(typeof listener === 'function') {

            this.listeners.push(listener)

        } else {

            throw new Error('listener 必須是 function')

        }

    }

    removeListener(listener) {

        this.listeners.splice(this.listeners.indexOf(listener), 1)

    }

    notify(message) {

        this.listeners.forEach(listener => {

            listener(message);

        })

    }

}

​

var egghead = new Producer(); 

// egghead 同時具有 註冊監聽者及移除監聽者 兩種方法

​

Rx.Observable

  .fromEventPattern((handler) => egghead.addListener(handler), (handler) => egghead.removeListener(handler))

  .subscribe(console.log)

​

egghead.notify('Hello! Can you hear me?');