usePrevious
usePrevious is a React hook that returns the previous value of the input state. It preserves the previous value unchanged when re-renders occur without state changes. If the state is an object or requires custom change detection, a compare function can be provided. By default, state changes are detected using prev === next.
Interface
ts
function usePrevious<T>(state: T, compare?: (prev: T, next: T) => boolean): T;Parameters
- staterequired · T
The state whose previous value is to be tracked.
- compare(prev: T, next: T) => boolean
An optional comparison function to determine if the state has changed.
Return Value
- T
The previous value of the state.
Example
tsx
const [count, setCount] = useState(0);
// initial value of previousCount is `0`
const previousCount = usePrevious(count);