code: function notify(oldVal, newVal) {
  	var count = 0;
          for (var key in watchers) {
  	  var watcher = watchers[key];
            watcher.call(this, key, oldVal, newVal);
            count++;
          }
  
          return count;
        }
docs: The use of named function exprs is a temporary hack to make these methods play nicely with `invoker`.  This is a non-portable technique.