一啃擦、概念
觀察者(observer)模式：又稱訂閱/發(fā)布(subscriber/publisher)模式酵熙，
被觀察者(也成發(fā)布者或者主題)
觀察者(也稱訂閱者)
當(dāng)發(fā)生特定事件時(shí)桅咆，發(fā)布者通知(調(diào)用)所有訂閱者王浴，以事件對(duì)象的形式傳遞消息斗遏。
通過(guò)這種方式山卦，促成松耦合。
二诵次、屬性及方法
subscribers : 記錄訂閱者的數(shù)組账蓉；
subscribe() : 將訂閱者添加到subscribers數(shù)組的方法；
unsubscribe() : 從訂閱者數(shù)組subscribers刪除訂閱者的方法逾一；
publish() : 循環(huán)遍歷subscribers數(shù)組铸本，調(diào)用每個(gè)訂閱者注冊(cè)時(shí)提供的方法。
三遵堵、實(shí)現(xiàn)

// 發(fā)布功能實(shí)現(xiàn)實(shí)例
    var publisher = {
        subscribers: {
            any: []
        },
        subscribe: function(fn, type) {
            type = type || 'any';
            if (typeof this.subscribers[type] === 'undefined') {
                this.subscribers[type] = [];
            }
            this.subscribers[type].push(fn);
        },
        unsubscribe: function(fn, type) {
            this.visitSubscribers('unsubscribe', fn, type);
        },
        publish: function(publication, type) {
            this.visitSubscribers('publish', publication, type);
        },
        visitSubscribers: function(action, arg, type) {
            var pubtype = type || 'any',
                subscribers = this.subscribers[pubtype],
                i,
                max = subscribers.length;
            for (i = 0; i < max; i++) {
                if (action === 'publish') {
                    subscribers[i](arg);
                } else {
                    if (subscribers[i] === arg) {
                        subscribers.splice(i, 1);
                    }
                }
            }
        }
    }
    // 將發(fā)布方法復(fù)制到傳入的對(duì)象中
    function makePublisher(o) {
        for(var i in publisher) {
            if (publisher.hasOwnProperty(i) && typeof publisher[i] === 'function') {
                o[i] = publisher[i];
            }
        }
        o.subscribers = {
            any: []
        }
    }
    // 測(cè)試
    var publish = {
        priceIncrease: function(flux) {
        this.publish('Price Increase :' + flux);
        },
        priceDecrease: function(flux) {
            this.publish('Price Decrease :' + flux);
        },
    }
    makePublisher(publish);

    var price = 100;
    var board = {
        // _price: 100,
        changePrice: function(content) {
            var flux = Number(content.split(":")[1]);
            price =  price + flux
            document.getElementById("priceSpan").innerHTML = price;
        },
        // getPrice: function() {
        //  return this._price;
        // }
    }
    publish.subscribe(board.changePrice);