No, that one doesn't stay either. Are you failing to see that the playButton already has
(button) as the function parameter? The function already has button defined as a function parameter. Replacing that button with another definition of the same button is worse than useless. Not only does that
var button line replace the button that's passed in to the function, it is a needless confusion to all developers looking at the code.
var button line fails to work as well.
Get rid of it.