feat: useDelay hook (#1808)

useDelay hook that returns true until a delay timeout has completed then
returns false.

resolves #1807

Author: bmingles

packages/react-hooks/src/index.ts

@@ -4,6 +4,7 @@ export * from './useAsyncInterval';
 export * from './useCallbackWithAction';
 export { default as useContextOrThrow } from './useContextOrThrow';
 export * from './useDebouncedCallback';
+export * from './useDelay';
 export * from './useDependentState';
 export * from './useEffectNTimesWhen';
 export * from './useIsEqualMemo';

packages/react-hooks/src/useDelay.test.ts

@@ -0,0 +1,55 @@
+import { act, renderHook } from '@testing-library/react-hooks';
+import { useDelay } from './useDelay';
+
+describe('useDelay', () => {
+  const delay500 = 500;
+  const delay1000 = 1000;
+  const delay2000 = 2000;
+
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  it('should return true while delay is active and false when done', () => {
+    const { result } = renderHook(() => useDelay(delay1000));
+    expect(result.current).toBe(true);
+
+    act(() => jest.advanceTimersByTime(delay1000));
+
+    expect(result.current).toBe(false);
+  });
+
+  it('should cancel setter when unmounted', () => {
+    const { result, unmount } = renderHook(() => useDelay(delay1000));
+    unmount();
+
+    act(() => jest.advanceTimersByTime(delay1000));
+
+    expect(result.current).toBe(true);
+  });
+
+  it('should reset when delayMs is changed', () => {
+    const { result, rerender } = renderHook(
+      ({ delayMs }) => useDelay(delayMs),
+      {
+        initialProps: { delayMs: delay1000 },
+      }
+    );
+
+    act(() => jest.advanceTimersByTime(delay500));
+
+    rerender({ delayMs: delay2000 });
+
+    act(() => jest.advanceTimersByTime(delay1000));
+
+    expect(result.current).toBe(true);
+
+    act(() => jest.advanceTimersByTime(delay1000));
+
+    expect(result.current).toBe(false);
+  });
+});

packages/react-hooks/src/useDelay.ts

@@ -0,0 +1,24 @@
+import { useEffect, useState } from 'react';
+
+/**
+ * Sets a delay, and returns a boolean indicating whether the delay is still active.
+ * @param delayMs The delay in milliseconds
+ * @returns A boolean indicating whether the delay is still active
+ */
+export function useDelay(delayMs: number): boolean {
+  const [isDelayed, setIsDelayed] = useState(true);
+
+  useEffect(() => {
+    const timeout = setTimeout(() => {
+      setIsDelayed(false);
+    }, delayMs);
+
+    return () => {
+      clearTimeout(timeout);
+    };
+  }, [delayMs]);
+
+  return isDelayed;
+}
+
+export default useDelay;