AI solution for React Quiz on BFE.dev
17. flushSync()

The code outputs the following to the console:

render 0
handler
handler 0
render 1

This is because when the component first renders, it logs "render 0". Then, when the button is clicked with userEvent.click(), the onClick function is called which logs "handler" and updates the state using flushSync() to increment it by 1. However, since setState() is asynchronous, the value of state inside the second console.log() still logs 0. Finally, after the state has been updated, the component re-renders with the updated state value of 1, which is why "render 1" is logged to the console.