設計模式之發佈/訂閱模式

原創

2020-02-22 00:37

<pre name="code" class="html"><html>
  <head>
    <title>Observer</title>
    <script type="text/javascript" src="js/jquery-1.12.4.min.js"></script>
  </head>
  <body>


    <script type="text/javascript">
      var pubsub = (function() {
        //訂閱者列表
        var events = {};
        var subUid = 0;
        //發佈
        function publish(eventName, args) {
          if (!events[eventName]) {
            return false;
          }
          var subscribers = events[eventName];
          var len = subscribers.length;
          while (len--) {
            subscribers[len].callback(eventName, args);
          }
        }
        //訂閱
        function subscribe(eventName, callback) {
          events[eventName] = events[eventName] || [];
          var id = subUid++;
          events[eventName].push({
            callback: callback,
            id: id
          });
          return id;
        }
        //取消訂閱
        function unsubscribe(id) {
          var eventName;
          var i;
          var len;
          var subscribers;
          for (eventName in events) {
            subscribers = events[eventName];
            if (subscribers) {
              for (i = 0, len = subscribers.length; i < len; i++) {
                if (subscribers[i].id === id) {
                  subscribers.splice(i, 1);
                  return id;
                }
              }
            }
          }
          return this;
        }
        //利用Revealing Module模式隱藏內部實現，提供接口
        return {
          publish: publish,
          subscribe: subscribe,
          unsubscribe: unsubscribe
        };
      }());
      //在hello事件生增加一個訂閱
      var subscription = pubsub.subscribe("hello", function(eventName, data) {
        console.log("Event:" + eventName + "/data:" + data);
      });
      //向訂閱者發送消息
      pubsub.publish("hello", ["天鑲"]);
      //向訂閱者發送消息
      pubsub.publish("hello", ["天鑲", "求", "offer"]);
      //取消訂閱
      pubsub.unsubscribe(subscription);
      //向訂閱者發送消息
      pubsub.publish("hello", ["天鑲", "再求", "offer"]);
    </script>
  </body>
</html>