Learning functional programming can be hard, especially if your mind is stuck for a long time in an object oriented world. Luckily there are some good books out there.
One book I can recommend to learn the concepts of functional programming is ‘Professor Frisby’s Mostly Adequate Guide to Functional Programming’. It’s a great resource with a lot of samples and small exercises. All examples in the book are using JavaScript which lowers the entry barrier as you don’t have to learn a new language.
Download the book here: