usePrevValue

Tracks the previous value of a state or prop. Returns undefined on the first render, then the value from the previous render cycle. Used internally by the Popover component.

Import

import { usePrevValue } from '@andrejground/lab';

Usage

import React from 'react';
import { usePrevValue } from '@andrejground/lab';

export default function App() {
  const [count, setCount] = React.useState(0);
  const prevCount = usePrevValue(count);

  return (
    <div>
      <button onClick={() => setCount((c) => c + 1)}>Increment</button>
      <p>Current: {count}</p>
      <p>Previous: {prevCount ?? 'N/A'}</p>
    </div>
  );
}

API

const previousValue = usePrevValue(value);

Parameter	Type	Description
value	T	The value to track

Returns

Type	Description
T | undefined	The value from the previous render, or undefined on the first render