The benefits of functional programming

Writing TypeScript code using a functional programming style has many benefits, among which we can highlight the following:

• Our code is testable: If we try to write our functions as pure functions, we will be able to write unit tests extremely easily. We will learn more about pure functions later in this chapter.
• Our code is easy to reason about: Functional programming can seem hard to understand for developers with a lack of experience in functional programming. However, when an application is implemented correctly using the functional programming paradigm, the results are very small functions (often one-line functions) and very declarative APIs that can be reasoned about with ease. Also, pure functions only work with their arguments, which means that when we want to understand what a function does, we only need to examine the function itself and we don't need to be concerned about any other external variables.
• Concurrency: Most of our functions are stateless, and our code is mostly stateless. We push state out of the core of our application, which makes our applications much more likely to be able to support many concurrent operations and it will be more scalable. We will learn more about stateless code later in this chapter.
• Simpler caching: Caching strategies to cache results become much simpler when we can predict the output of a function given its arguments.