The last step to take is to learn how we can use FP to build UIs, which is what we use React for.

We can think about a UI as a function to which is applied the state of the application, as follows:

  UI = f(state);

We expect this function to be idempotent so that it returns the same UI given the same state of the application.

Using React, we create our UIs using components we can consider functions, as we will see in the following chapters.

Components can be composed to form the final UI, which is a property of FP.

There are a lot of similarities in the way we build UIs with React and the principles of FP, and the more we are aware of it, the better our code will be.