Stop implementing date pickers when <input type="date"> exists.
Stop implementing smooth scrolling. Browsers already do it on their own, and your implementation will not work. Really, just don't mess with scrolling in general. Don't make scrolling have "momentum". Don't change scroll speed. One site I've been to goes out of its way to change how much a scroll wheel click scrolls the page. For fuck's sake, can someone explain to me why that would be a feature!? Why go out of your way to override a specific user preference!?
All this bullshit changes expected behaviors, reduces accessibility, reduces the performance of your web page (and therefore increases CPU and battery usage)...for no reason whatsoever.