return on useeffect code example

Example 1: useeffect umnount

useEffect(() => {
    return () => {
      console.log("cleaned up");
    };
  }, []);

Example 2: how to have a function inside useeffect

useEffect(() => {
  fetch(`https://jsonplaceholder.typicode.com/${query}`)
    .then(response => response.json())
    .then(json => setData(json));
}, [query]); // only re-run on query change