isNaN [JavaScript snippet]

function fnIsNaN(n) {
  txt_out(n + ' is ' + (isNaN(n) ? 'not ' : '' ) + 'a number');
}

function main() {
  fnIsNaN( 5       );
  fnIsNaN( 5.5     );
  fnIsNaN("5.5"    );
  fnIsNaN("abc"    );
  fnIsNaN(NaN      );
  fnIsNaN("  42"   );
  fnIsNaN("  42 ! ");
  fnIsNaN(" #42   ");
}