useEffectWithPreviousValues

Function

useEffectWithPreviousValues(callback: (preValues: readonlyunknown[]) => void, dependencies: readonlyunknown[]): void

Wrapper of useEffect, the callback can get the previous values of dependencies.

Parameters

Parameter Type Notes

callback (preValues: readonlyunknown[]) => void

Parameter	Type	Notes
`callback`	(preValues: readonlyunknown[]) => void
`dependencies`	readonlyunknown[]	dependencies must be a non-empty array and the length should not change example: Use dark colors for code blocksCopy `1 2 3 4 5 6 7 8 9 10 11 12 13 14 const [count, setCount] = useState(0) const [opened, setOpened] = useState(false) useEffectWithPreviousValues((preValues) => { const [preCount, preOpened] = preValues if (count !== preCount) { console.log('count changes') } if (opened !== preOpened) { console.log('opened changes') } }, [count, opened)`

dependencies

readonlyunknown[]

dependencies must be a non-empty array and the length should not change

example:

Use dark colors for code blocksCopy
const [count, setCount] = useState(0)
const [opened, setOpened] = useState(false)

useEffectWithPreviousValues((preValues) => {
 const [preCount, preOpened] = preValues

 if (count !== preCount) {
   console.log('count changes')
 }

 if (opened !== preOpened) {
   console.log('opened changes')
 }
}, [count, opened)

Returns

void