React 的 useState 是如何改变常量的值的？

Question

This is the syntax I'm working with.

const [count, setCount] = useState(0);
const handleIncrement = () => {
    setCount((count + 1));
  };

I understand that setCount is creating an instance of count, but I'm really not grasping how exactly count is being changed if it's a constant or how, if it's an instance, it's able to be called and return the most recent value.

Wouldn't every time React re-renders the page, it reads the constant count first?

It's working just fine for me, but I can't wrap my head around why.

Answer 1

count is 'constant' for the duration of the function. When setCount() is called, the local count doesn't change. Eventually your component gets rendered again with the new value.

During this new render the count is updated, but it will again be constant for the duration of the render/function.