4 ms·

Fairly common: triggering a side-effect that uses some state value, only when a different piece of state changes. useEffect(() => { doSomething(someState) },

• jhardy54 2y ago
  Sorry, there might be a misunderstanding —- I’m looking for an example of when the dependency array needs to be [], is that what you posted?
  • beedrillzzzzz 2y ago
    Yeah maybe I didn’t follow exactly, I meant this as a common example of when the hook dependencies rules must be ignored.
  • naught0 2y ago
    The example supplied is what I was trying to get at. An empty dependency array means that the effect runs only once on mount. Same with memos and callbacks -- the value should remain stable. Here's a real world example of how I populate some state based on url query params: https://github.com/Naught0/combinator/blob/master/frontend/src/App.tsx#L36-L53 https://github.com/Naught0/combinator/blob/master/frontend/s... I may end up using a more robust routing solution to keep in sync with query params if I ever want to spend the effort, but this is a naive solution that works alright. A more simplified, generic example could be: const [foo, setFoo] = useState(); useEffect(() => { setFoo("bar"); }, []); // The eslint rule wants setFoo here despite the value being stable