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<!DOCTYPE html>
<html>
<head>
<meta name="description" content="[iterator & observer]">
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

<script id="jsbin-javascript">
var Subject = function() {
  var self = this;
  self.observers = [];

  return {
    subscribe: function(observer) {
      self.observers.push(observer);
    },
    unsubscribe: function(observer) {
      var index = self.observers.indexOf(observer);
      if (index > -1) {
        self.observers.splice(index, 1);
      }
    },
    notify: function(observer) {
      var index = self.observers.indexOf(observer);
      if (index > -1) {
        self.observers[index].notify(index);
      }
    },
    notifyAll: function() {
      for (var i = 0; i < self.observers.length; i++) {
        self.observers[i].notify(i);
      }
    },
    notifyIterator: function() {
        var i = 0;
        return {
            next: function(){
               return i < self.observers.length ?
               {value: self.observers[i++].notify(i), done: false}:
               {done: true};
            }
        };
    }
  };
};

var Observer = function() {
    return {
      notify: function(index) {
        console.log("Observer " + (index) + " is notified!");
      }
    }
  }

  var subject = new Subject();

  var observer1 = new Observer();
  var observer2 = new Observer();
  var observer3 = new Observer();
  var observer4 = new Observer();

  subject.subscribe(observer1);
  subject.subscribe(observer2);
  subject.subscribe(observer3);
  subject.subscribe(observer4);


var it = subject.notifyIterator();
 it.next().value;
 it.next().value;
 it.next().value;
 it.next().value;
 console.log(it.next().done);
</script>


<script id="jsbin-source-javascript" type="text/javascript">var Subject = function() {
  var self = this;
  self.observers = [];

  return {
    subscribe: function(observer) {
      self.observers.push(observer);
    },
    unsubscribe: function(observer) {
      var index = self.observers.indexOf(observer);
      if (index > -1) {
        self.observers.splice(index, 1);
      }
    },
    notify: function(observer) {
      var index = self.observers.indexOf(observer);
      if (index > -1) {
        self.observers[index].notify(index);
      }
    },
    notifyAll: function() {
      for (var i = 0; i < self.observers.length; i++) {
        self.observers[i].notify(i);
      }
    },
    notifyIterator: function() {
        var i = 0;
        return {
            next: function(){
               return i < self.observers.length ?
               {value: self.observers[i++].notify(i), done: false}:
               {done: true};
            }
        };
    }
  };
};

var Observer = function() {
    return {
      notify: function(index) {
        console.log("Observer " + (index) + " is notified!");
      }
    }
  }

  var subject = new Subject();

  var observer1 = new Observer();
  var observer2 = new Observer();
  var observer3 = new Observer();
  var observer4 = new Observer();

  subject.subscribe(observer1);
  subject.subscribe(observer2);
  subject.subscribe(observer3);
  subject.subscribe(observer4);


var it = subject.notifyIterator();
 it.next().value;
 it.next().value;
 it.next().value;
 it.next().value;
 console.log(it.next().done);
</script></body>
</html>