Why angular can't deal with NaN value passed to directive?

[Artur Nowakowski]

I've tried to answer the question on stackoverflow (http://stackoverflow.com/questions/24271524/angular-js-nan-handling) and I've seen strange behavior of angular directive when NaN value is passed to directive's scope. I can't explain why does it happen, so maybe you could explain it to me. 

It's the directive code:

.directive('test',function(){

    return{

        restrict: 'E',

        template: '<span>Test directive number = {{number}}</span>',

        scope: {

            number: '='    

        },

        link: function(scope,elem,attrs){            

           scope.number = scope.number || 10;

        }

    }

});

If I pass NaN as number attribute, link function cannot manipulate with "scope.number" variable. If I try to change its value even by simply "scope.number = 5", nothing happens. 

Is it a bug in angular or an expected behavior? Why does it happen?

Here is the fiddle: http://jsfiddle.net/aartek/k2r9F/

[raju reddy]

Hi,

 Hope you restricted to element,Can you change and try it