Your useEffect is executed only once per render cycle, but you have several state updates in your useEffect which cause a re-render. Hence you get a lot of alerts. See a demo of your code and see the console.logs as well as comments Also note that useEffect will when you provide empty array dependency, your … Read more
I can’t answer the “should you” part of whether to use refs for this instead other than if you do, you don’t need those id values unless you use them for something else. But here’s how you would: Use useRef(null) to create the ref. const activeSlideRef = useRef(null); Put it on the Slide that’s currently … Read more
You need to clear your interval, useEffect(() => { const intervalId = setInterval(() => { //assign interval to a variable to clear it. setState(state => ({ data: state.data, error: false, loading: true })) fetch(url) .then(data => data.json()) .then(obj => Object.keys(obj).map(key => { let newData = obj[key] newData.key = key return newData }) ) .then(newData => … Read more
You can’t configure it out of the box. But, a common pattern is to use some isMounted flag like so: // Is Mounted const useFetchNotOnMount = () => { … const isMounted = useRef(false); useEffect(() => { if (isMounted.current) { console.log(‘fetching’); dispatch(fetchData(filters)); } else { isMounted.current = true; } }, [dispatch, filters]); }; // Same … Read more
The pattern that you need to follow depends on your use case. First: You might have a situation where you need to add event listener during the initial mount and clean them up at unmount and another case where a particular listener needs to be cleaned up and re-added on a prop change. In such … Read more
This behaviour is from React 18 itself when you are in development with Strict Mode. The core team is trying to implement this feature where we can preserve components’ state even after unmount. useEffect getting called twice is related to this feature. Here is an overview of what they say in the doc: In the … Read more
It’s not quite the same. Giving it an empty array acts like componentDidMount as in, it only runs once. Giving it no second argument acts as both componentDidMount and componentDidUpdate, as in it runs first on mount and then on every re-render. Giving it an array as second argument with any value inside, eg , … Read more
If you only want to run the function given to useEffect after the initial render, you can give it an empty array as second argument. function MyComponent() { useEffect(() => { loadDataOnlyOnce(); }, []); return <div> {/* … */} </div>; }