Fundamentals of functional programming with React

Functional programming is a key concept for React developers, often overlooked by beginners, that can simplify testing and maintenance of applications by emphasizing pure functions and immutability. Pure functions in functional programming, like mathematical functions, produce the same output for the same input and do not cause side effects, such as modifying global variables, which can lead to bugs. In React, pure functions manifest in components that render predictable outputs based on their props, and React.memo can optimize performance by preventing unnecessary re-renders. State updates in React also leverage functional programming by using updater functions that rely on previous state values. Additionally, React uses the useEffect hook to manage side effects separately from rendering logic. The concept of function composition in mathematics is mirrored in React through component composition, which allows developers to build complex components by combining smaller ones, enhancing reusability and customization. This approach, alongside the principles of immutability and avoiding side effects, forms the foundation of functional programming in React, improving application performance and maintainability.