React useEffect causing: Can't perform a React state update on an unmounted component

Question

When fetching data I\'m getting: Can\'t perform a React state update on an unmounted component. The app still works, but react is suggesting I might be causing a memory leak

Answer 1

Sharing the AbortController between the fetch() requests is the right approach.
When any of the Promises are aborted, Promise.all() will reject with AbortError:

function Component(props) {
  const [fetched, setFetched] = React.useState(false);
  React.useEffect(() => {
    const ac = new AbortController();
    Promise.all([
      fetch('http://placekitten.com/1000/1000', {signal: ac.signal}),
      fetch('http://placekitten.com/2000/2000', {signal: ac.signal})
    ]).then(() => setFetched(true))
      .catch(ex => console.error(ex));
    return () => ac.abort(); // Abort both fetches on unmount
  }, []);
  return fetched;
}
const main = document.querySelector('main');
ReactDOM.render(React.createElement(Component), main);
setTimeout(() => ReactDOM.unmountComponentAtNode(main), 1); // Unmount after 1ms