call a function once in useeffect code example

Example 1: react run useeffect only once

useEffect(() => {
    // Initialization code comes here
}, []);

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