AI solution for React Quiz on BFE.dev
16. event callback

The code outputs the following by console.log:

render 0
handler
render 1
handler 0

The first console.log statement is from the initial render, where the state is 0.

After clicking the button, the component is re-rendered, and the state is updated to 1. The second console.log statement is from the onClick handler function, which is called when the button is clicked. It shows the previous value of state, which is 0, because the setState function is asynchronous and hasn't updated the state yet.