{} inside useEffect?

Asked Nov 02 '21 at 13:23

Active Nov 02 '21 at 13:44

Viewed 56 times

I've found the following snippet in an application. What's the meaning of the double () in this snippet? What effect does it have? It'd seem it's a function that calls function, but why?

useEffect(
    () => () => {
      dispatch(fetchData());
    },
    []
  );

Thanks

edited Nov 02 '21 at 13:44

isherwood

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asked Nov 02 '21 at 13:23

Wasteland

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its a function that returns a function. – Daniel A. White Nov 02 '21 at 13:24
1

indeed. So it means that when the component gets unmounted, fetchData is called – fredericrous Nov 02 '21 at 13:26
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`() => () => {/* body */}` is an arrow function that returns a function when called. Together with `useEffect` and an empty dependency list that means that the returned function will be called when the component unmounts. – trixn Nov 02 '21 at 13:26
Thanks - duuuh - I didn't spot it's a cleanup function in this context! – Wasteland Nov 02 '21 at 13:28

What's the meaning of () => () => {} inside useEffect?

0 Answers0