Libraries/packages I find useful are:
(in no particular order or in anyway complete)
LoDash and/or Ramda are somewhat indispensable, although they are not the only players in that space, I tend to resort to either of those two for most projects.
Date-fns and DayJS provide a good alternative to MomentJS and there's a few others in this space also worthy of a look.
Cash, a good alternative to jQuery, when you don't have to use jQuery by force (not that there is anything wrong with jQuery, it has its place and purpose and serves them well).
jQuery MatchHeight is something I use reguarly in jQuery based builds, for example WordPress. It's a nice little plugin for equal height columns/rows.
I ought to dig through my archives sometime and put together a more formal list of alternatives. There's quite a lot out there in the ecosystem.
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