React Fiber: A Simple Use Case for Controlled Input

In React, like any time you update the state, React will try to rerender the UI so it'll run your render function again. And some things, if you could say these things are really high priority, don't interrupt the render of this in order to render something else. Then React can schedule when it runs the render in smarter ways,. It can let batch updates together and it can do stuff like that.