setState-on-unmounted-component.md

Error "setState on unmounted component" occurs occasionally

• Established workaround: CodeSandBox: Observe useEffect with empty dependency array (JS)

Scenario:

async function handleSubmit() {
    setPending(true)
    await post('/someapi') // component might unmount while we're waiting
    setPending(false)
}

This is a workaround (see sandbox above):

useEffect(() => {
    function handleChange() {
        setState(store.getState())
    }
    store.subscribe(handleChange)
    return () => store.unsubscribe(handleChange)
}, [])

• This handles out-of-order responses with a ref (or local variable if dependency array is empty array)
• It's discussed to remove the warning in this GitHub issue.