React.useState ​

💡 Hooki są zajebiste. - Łukasz Pluszczewski

const [variable, setVariable] = useState(initialValue)

To setVariable function we can pass both value and the function that takes previous value as the argument. The calculated value will be set to the hooked variable:

setVariable(5);
setVariable((prevValue) => prevValue + 1);

React's' useState and setState don’t make changes directly to the state. They create queues to optimise performance, which is why the changes don’t update immediately. The process to update React state is asynchronous for performance reasons.

The useState hook cannot be called conditionally. The exact number of calls and the order of the calls have to be the same in every component render. They can be used in callbacks, in loops, in another functions.

An exception: hooks may be used in custom hooks.

To perform side effects after state has change, you must use the useEffect.