usePrevious

Remember the value of a variable from the previous render.

Usage#

import { usePrevious } from '@primereact/hooks/use-previous';

const [count, setCount] = React.useState(0);
const prev = usePrevious(count);
 
React.useEffect(() => {
    if (prev !== undefined && prev !== count) {
        console.log(`changed from ${prev} to ${count}`);
    }
}, [count, prev]);

Returns null on the first render, then the value from the prior render on every subsequent render.

Signature#

function usePrevious<T>(value: T): T | null | undefined;