Functional programming concepts in JavaScript such as pure functions, immutable data, and higher-order functions are difficult for most developers due to their imperative programming habits, lack of understanding modern JavaScript features, and an aversion to learning underlying functional math concepts. Understanding core functional utilities like map, filter, reduce, and zip as well as concepts like functors, applicatives, and monads requires overcoming years of imperative thinking and a willingness to understand concepts rather than just code. Reading Ramda tests and Fantasy Land specifications can help familiarize developers with a functional style of programming.