The observer pattern for JavaScript design patterns

The Observer pattern is also known as the Publish/subscribe mode Publish/subscribe

It is a one-to-many relationship that allows multiple observer objects to listen to a Subject object at the same time, which notifies all observer objects when their state changes, enabling them to automatically update themselves.

1 functionMsgbus () {2 3     varMsgmap = {};//Internal message bus4     varInstance = {};5 6 7     /**8 * @function Subscribe9 * @description Subscribe message listener.Ten * @param msgtype {string}-message type to be listen. One * @param handler {function}-handler function when the message sent. A * @instance -      */ -Instance.subscribe =function(msgtype,handler) { the         if(Msgtype = =NULL){ -Console.error ("Message type is null"); -             returninstance; -         } +         if(Handler = =NULL){ -Console.error ("Handler is null"); +             returninstance; A         } at         varSubscribearray =Msgmap[msgtype]; -         if(Subscribearray = =NULL){ -Subscribearray =NewArray (); -Msgmap[msgtype] =Subscribearray; -         } -         if(Subscribearray.indexof (handler) < 0){ in Subscribearray.push (handler); -         } to         returninstance; +     } -  the     /** * * @function Unsubscribe $ * @description Unsubscribe message listener.Panax Notoginseng * @param msgtype {string}-message type to be unsubscribe. - * @param handler {function}-handler function to is removed. the * @instance +      */ A  theInstance.unsubscribe =function(msgtype,handler) { +         varSubscribearray =Msgmap[msgtype]; -         if(Subscribearray! =NULL){ $             varindex =Subscribearray.indexof (handler); $             if(Index > 0){ -Subscribearray.splice (index,1); -             } the         } - Wuyi         returninstance; the     } -  Wu  -     /** About * @function Publish $ * @description publish message. - * @param msgtype {string}-message type to be published. - * @param data {Object}-message data. - * @instance A      */ +Instance.publish =function(msgtype,data) { the         varSubscribearray =Msgmap[msgtype]; -         if(Subscribearray = =NULL){ $             return; the         } the          for(vari=0;i<subscribearray.length;i++){ the             Try{ the Subscribearray[i] (data); -}Catch(e) { inConsole.error ("error when sending Message:" +msgtype); the             } the         } About  the         returninstance; the     } the  +     returninstance; -}

Test it:

var instance = Msgbus (); Instance.subscribe ("subscribe",function(data) {Console.log (" "+ Data"}); Instance.publish (// This is cangjingkong

The observer pattern for JavaScript design patterns