I fell in love with Yoo In-dong and functional programming after coming into contact with artistic JS code through the book Functional JavaScript Programming. So I took the free lecture, but after watching FEConf's seminar, I felt the need for a paid lecture, so I paid. I like to buy programming books even for their collection value, but I was reluctant to buy online lectures. However, after this lecture, I paid for the application version right away and I started to trust Inflearn lectures. I think it's no exaggeration to say that Yoo In-dong's book and lectures have changed my development values. I always look at the fxjs reference on my way to and from work, and I also study lodash and lambda, so I'm going to try proper functional JavaScript programming!