javascript - How does angular.equals evaluate invalid date objects? -

i understand shouldn't using invalid date objects compare each other, purposes of understanding how , why angular.equal handles

angular.equals(new date(''), new date('')); //returns false, both objects null 

on other hand

angular.equals(null, null); //returns true 

what missing here? jsfiddle if feel need

if using angular <1.2.x see behavior. because .equals implementation checks equality of p1.gettime() , p2.gettime() in case nan , nan not nan. 1.2.x onwards has been changed there recursive check again on .equals , there condition:

 if (o1 !== o1 && o2 !== o2) return true; // nan === nan 

which see value returning true in case.

>=1.2.x

  else if (isdate(o1)) {     if (!isdate(o2)) return false;     return equals(o1.gettime(), o2.gettime()); //returns false   } 

<1.2.x

 else if (isdate(o1)) {     return isdate(o2) && o1.gettime() == o2.gettime(); //returns true   }