React hook for remembering a previous value.
npm install react-use-previousReact hook for remembering a previous value.
``sh`
npm install --save react-use-previous
This hook is similar to the one mentioned in the docs, but it returns a ref instead of the actual value, so that you can use this anywhere, even if some functions are cached.
`ts
import {useState} from 'react';
import usePrevious from 'react-use-previous';
function useFoo () {
const [value, setValue] = useState ( 0 );
const prevValue = usePrevious ( value );
useEffect ( () => {
function update () {
// This function is cached, since this useEffect has no dependencies and gets only executed when mounting and unmounting
// But it can still access the previous value
const nextValue = Math.random ();
if ( nextValue !== prevValue.current ) setValue ( nextValue );
}
$(window).on ( 'resize', update );
return () => $(window).off ( 'resize', update );
}, [] );
return value;
}
``
MIT © Fabio Spampinato