I would probably structure the problem like this:

    var ans = someCalculation(x,y);
    
    if (truthy(ans) && !isNaN(ans))
      //do something
    else
      //do something else

The point being I like to dispatch conditions on boolean results of certain properties of my results rather than the result directly. It helps me to keep my sanity.

Thanks for the kind words BTW. :-)