use-previous

1import { useRef } from 'react'
2 
3export type ShouldUpdateFunc<T> = (prev?: T, next?: T) => boolean
4 
5const defaultShouldUpdate = <T>(a?: T, b?: T) => !Object.is(a, b)
6 
7function usePrevious<T>(
8  state: T,
9  shouldUpdate: ShouldUpdateFunc<T> = defaultShouldUpdate,
10): T | undefined {
11  const prevRef = useRef<T>(undefined)
12  const curRef = useRef<T>(undefined)
13 
14  if (shouldUpdate(curRef.current, state)) {
15    prevRef.current = curRef.current
16    curRef.current = state
17  }
18 
19  return prevRef.current
20}
21 
22export default usePrevious