?定義

定義一對多的對象封裝，目標對象狀態發生變化，它所有的接受者都會收到通知并做相應的更新。

使用頻率：5/5 最高

概要

觀察者模式，也就是發布者/訂閱者模式，當發布者發布一個通知的時候，訂閱者就會收到通知，并調用自己的更新方法，做些什么事情。這種通知是單向的，只能由發布者向訂閱者發布通知。

圖標說明

示例代碼

      var Publisher = function () {
        this.subscribers = [];
      }

      Publisher.prototype = {

          constructor: Publisher,

          addSubscriber: function(subscriber){
            this.subscribers.push(subscriber);
          },

          removeSubscriber: function(subscriber){
            var subscribers = this.subscribers,
              len = subscribers.length,
              i = 0;
            for(; i < len; i++){
              if (subscribers[i] === subscriber) {
                delete subscribers[i];
                break;
              };
            }
          },

          notifySubscriber: function(message){
            var subscribers = this.subscribers,
              len = subscribers.length,
              i = 0;
            for(; i< len; i++){
              subscribers[i].receiveMessage(message);
            }
          }
      };

      var Subscriber = function(subscriberName, publisher){
        this.name = subscriberName;
        this.publisher = publisher;
      };

      Subscriber.prototype = {

        constructor: Subscriber,

        receiveMessage: function(message){
          console.log('I am ' + this.name + ' I receive: ' + message);
        }
      };

      var publisher = new Publisher();
      var subUser_001 = new Subscriber('subUser_001', publisher);
      var subUser_002 = new Subscriber('subUser_002', publisher);
      var subUser_003 = new Subscriber('subUser_003', publisher);

      publisher.addSubscriber(subUser_001);
      publisher.addSubscriber(subUser_002);
      publisher.addSubscriber(subUser_003);

      publisher.notifySubscriber('百度推送新聞了');

轉載于:https://www.cnblogs.com/wylking2000/p/3244010.html

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