Nomenclature in React

In React, it’s conventional to use onSomething names for props which represent events and handleSomething for the function definitions which handle those events.

The export JavaScript keyword makes this function accessible outside of this file. The default keyword tells other files using your code that it’s the main function in your file.

Functions starting with use are called Hooks. useState is a built-in Hook provided by React. You can find other built-in Hooks in the API reference. You can also write your own Hooks by combining the existing ones.

Hooks are more restrictive than other functions. You can only call Hooks at the top of your components (or other Hooks). If you want to use useState in a condition or a loop, extract a new component and put it there.