text: function observable(value) { 
    var subscribers = []; 
  
    function notify(newValue) { 
        for (var i = 0; i < subscribers.length; i++) { 
          subscribers[i](newValue); 
        } 
    } 
  
    function accessor(newValue) { 
      if (arguments.length && newValue !== value) { 
        value = newValue; 
        notify(newValue); 
      } 
      return value; 
    } 
  
    accessor.subscribe = function(subscriber) { 
      subscribers.push(subscriber); 
    }; 
  
    return accessor; 
  }