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useDebouncedCallback: add a flush method to returned callback #7272

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Original file line number Diff line number Diff line change
Expand Up @@ -26,4 +26,52 @@ describe('@mantine/hooks/use-debounced-callback', () => {
jest.advanceTimersByTime(100);
expect(callback).toHaveBeenCalledWith(3);
});

it('can be flushed immediately', () => {
const callback = jest.fn();
const { result } = renderHook(() => useDebouncedCallback(callback, 100));
result.current(1);
result.current(2);
result.current(3);
result.current.flush();
expect(callback).toHaveBeenCalledWith(3);
});

it('can flush on unmount', () => {
const callback = jest.fn();
const { result, unmount } = renderHook(() => useDebouncedCallback(callback, {delay : 100, flushOnUnmount : true}));
result.current(1);
result.current(2);
result.current(3);
unmount();
expect(callback).toHaveBeenCalledWith(3);
});


it('does not call after unmount if timer lapsed', () => {
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this adds a test for the clearTimeout functionality in the useEffect, previously untested, not strictly related to this change :)

const callback = jest.fn();
const { result, unmount } = renderHook(() => useDebouncedCallback(callback, {delay : 100, flushOnUnmount : false}));
result.current(1);
unmount();
jest.advanceTimersByTime(100);
expect(callback).not.toHaveBeenCalled();
});

it('does not call on unmount if never called', () => {
const callback = jest.fn();
const { unmount } = renderHook(() => useDebouncedCallback(callback, {delay : 100, flushOnUnmount : true}));
unmount();
expect(callback).not.toHaveBeenCalled();
});

it('does not call on unmount if already called and not called since', () => {
const callback = jest.fn();
const { result, unmount } = renderHook(() => useDebouncedCallback(callback, {delay : 100, flushOnUnmount : true}));
result.current(1);
jest.advanceTimersByTime(100);
expect(callback).toHaveBeenCalled();
callback.mockClear();
unmount();
expect(callback).not.toHaveBeenCalled();
});
});
Original file line number Diff line number Diff line change
@@ -1,19 +1,41 @@
import { useCallback, useEffect, useRef } from 'react';
import { useCallbackRef } from '../use-callback-ref/use-callback-ref';

const noop = () => {};

export function useDebouncedCallback<T extends (...args: any[]) => any>(
callback: T,
delay: number
options: number | { delay: number; flushOnUnmount?: boolean }
) {
const delay = typeof options === 'number' ? options : options.delay;
const flushOnUnmount = typeof options === 'number' ? false : options.flushOnUnmount;
const handleCallback = useCallbackRef(callback);
const debounceTimerRef = useRef(0);
useEffect(() => () => window.clearTimeout(debounceTimerRef.current), []);

return useCallback(
const lastCallback = Object.assign(useCallback(
(...args: Parameters<T>) => {
window.clearTimeout(debounceTimerRef.current);
debounceTimerRef.current = window.setTimeout(() => handleCallback(...args), delay);
const flush = () => {
if (debounceTimerRef.current !== 0) {
debounceTimerRef.current = 0;
handleCallback(...args);
}
};
lastCallback.flush = flush;
debounceTimerRef.current = window.setTimeout(flush, delay);
},
[handleCallback, delay]
), {flush : noop});

useEffect(
() => () => {
window.clearTimeout(debounceTimerRef.current);
if (flushOnUnmount) {
lastCallback.flush();
}
},
[lastCallback, flushOnUnmount]
);

return lastCallback;
}
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