Component Lifecycle: Mounting

It causes an error because setState is not allowed in componentDidMount
It triggers a re-render before the browser updates the screen
Calling setState() inside componentDidMount() is valid and will trigger an extra rendering, but it happens before the browser updates the screen. This means the user won't see the intermediate state, although the component will render twice in this cycle, potentially affecting performance.
It has no effect during the mounting phase
It waits until the next update cycle to apply changes