Introduction to Functional Programming in JavaScript

1. Benefits of Functional Programming
2. Pure Functions & Side-Effects
3. Point-Free style
4. Function Composition

Benefits of functional programming

• Useful patterns tested and proven along the years
• "Code that you don't understand is code that you cannot trust"
• Less to read
• Improve the readability of the code

Pure Functions & Side-Effects

• All functions are procedures but not all procedures are functions
• Side-effects make a code a lot harder to read and to reason about
• There is no useful program with no Side-effects
• Avoid Side-effects wherever possible

Point-Free style

• The map between the parameter and the argument
• The intent of Point-Free style is that most of your code doesn't have points, there are points but we collect those points into well known, established, provable, verifiable utilities.

Function Composition

• Make the steps of data transformation as obvious as possible
• Partial application and Currying are different techniques to make a specialized version of a generalized function

Resources

FP course by Kyle Simpson

Functional-Light JavaScript