As long as you use either the dry or wet refill cloths for the Swiffer the Swiffer will clean your hardwood floors without damaging or ruining the hardwood floors.
As long as the hardwood floors are finished hardwood floors the Swiffer will not ruin the floors but if the hardwood floors are not finished then I would not recommend using the Swiffer on the hardwood floors until you finish the hardwood floors first.
I have finished hardwood floors myself and use A Swiffer on the hardwood floors without a problem and it keeps them shining.
You can also use vinegar and water to mop the hardwood floors and help keep them shiny and clean.
Or even Pinesol is another good cleaning solution to keep hardwood floors shiny, clean and even smelling good.