javascript設計模式之觀察者模式

js的設計模式分為建立型模式，結構型模式和行為模式

行為模式描述了物件之間的通訊行為。

觀察者模式又叫釋出–訂閱模式，是一種常見的行為模式。

下面是示例程式碼：

// obesever mode
var observer = {
  // add a subscriber
  addSubscribes:function (callback){
    if(typeof callback === 'function'){
      this.subscribes[this.subscribes.length] = callback;
    }
  },

  // remove a subscriber
 

  removeSubscribes:function (callback){
    for (var i = this.subscribes.length - 1; i >= 0; i--) {
      if(typeof this.subscribes[i] === callback){
        delete this.subscribes[i];
      }
    }
  },

  // publish event
  publish:function (what){
    for (var i = this.subscribes.length - 1; i >= 0
 
; i--) {
      if(typeof this.subscribes[i] === 'function'){
        this.subscribes[i](what);
      }
    }
  },

  // turn an object into a observer
  make:function (o){
    for(var i in this){
      if(this.hasOwnProperty(i)){
        o[i] = this[i];
        o.subscribes = [];
      }
    }
  }
};

var
 
 blogger = {
  writeBlogPost:function (){
    var content = 'hello' + new Date();
    this.publish(content);
  }
};

var la_time = {
  newIssue:function (){
    var issue = 'Martians has landed on Earth!';
    this.publish(issue);
  }
};

observer.make(blogger);
observer.make(la_time);

var jack = {
  read:function (what){
    console.log('I have just read' + what);
  }
};

var jill = {
  learn:function (what){
    console.log('I also have read an new issue:' + what);
  }
};

blogger.addSubscribes(jack.read);
la_time.addSubscribes(jill.learn);
blogger.writeBlogPost();
la_time.newIssue();

下面是輸出結果：

I have just readhelloTue May 02 2017 14:43:49 GMT+0800 (CST)
VM481517:63 I also have read an new issue:Martians has landed on Earth!