Kyle Simpson who is probably most famous for his You don't know JS series has a great introduction book into functional programming in JS.
I read this book years ago (not realising who wrote it) and thought it was great. I then saw Kyle Simpson's video course on functional programming in JS on Frontend Masters, and made the link who the author of this book is.
I had very little background info on functional programming, and this book was the perfect introduction book into core functional programming techniques. It isn't too heavy on the maths side and takes a practical approach to teaching functional programming.
Even if you do not intend on writing functional JS any time soon I would still recommend you read his book. It is an easy read, interesting, and you will almost certain learn a lot.