feat: add useDebouncedValue hook

Author: thebuilder

README.md

@@ -26,6 +26,23 @@ npm install @charlietango/hooks --save
 All the hooks are exported on their own, so we don't have a barrel file with all the hooks.
 This guarantees that you only import the hooks you need, and don't bloat your bundle with unused code.
 
+### `useDebouncedValue`
+
+Debounce a value. The value will only be updated after the delay has passed without the value changing.
+
+```ts
+import { useDebouncedValue } from "@charlietango/hooks/use-debounced-value";
+
+const [debouncedValue, setDebouncedValue] = useDebouncedValue(
+  initialValue,
+  500,
+);
+
+setDebouncedValue("Hello");
+setDebouncedValue("World");
+console.log(debouncedValue); // Will log "Hello" until 500ms has passed
+```
+
 ### `useDebouncedCallback`
 
 Debounce a callback function. The callback will only be called after the delay has passed without the function being called again.

src/__tests__/useDebouncedValue.test.tsx

@@ -0,0 +1,79 @@
+import { act, renderHook } from "@testing-library/react";
+import { afterEach, beforeAll } from "vitest";
+import { useDebouncedValue } from "../hooks/useDebouncedValue";
+
+beforeAll(() => {
+  vi.useFakeTimers();
+});
+
+afterEach(() => {
+  // Should be no pending timers after each test
+  expect(vi.getTimerCount()).toBe(0);
+});
+
+test("should update the value after the delay", async () => {
+  const initialValue = "hello";
+  const { result } = renderHook(() => useDebouncedValue(initialValue, 500));
+
+  expect(result.current[0]).toBe(initialValue);
+  result.current[1]("world");
+  act(() => {
+    vi.runAllTimers();
+  });
+
+  expect(result.current[0]).toBe("world");
+});
+
+test("should skip old value", async () => {
+  const initialValue = "hello";
+  const { result } = renderHook(() => useDebouncedValue(initialValue, 500));
+
+  expect(result.current[0]).toBe(initialValue);
+  result.current[1]("new");
+  act(() => {
+    vi.advanceTimersByTime(250);
+  });
+
+  expect(result.current[0]).toBe(initialValue);
+
+  result.current[1]("world");
+  act(() => {
+    vi.runAllTimers();
+  });
+
+  expect(result.current[0]).toBe("world");
+});
+
+test("should update if 'initial value' is changed", async () => {
+  const { result, rerender } = renderHook((initialValue = "hello") =>
+    useDebouncedValue(initialValue, 500),
+  );
+
+  expect(result.current[0]).toBe("hello");
+  rerender("world");
+
+  act(() => {
+    // Should have triggered the update, when the value changes
+    expect(vi.getTimerCount()).toBe(1);
+    vi.runAllTimers();
+  });
+
+  expect(result.current[0]).toBe("world");
+});
+
+test("should update the value immediately if leading is true", async () => {
+  const initialValue = "hello";
+  const { result } = renderHook(() =>
+    useDebouncedValue(initialValue, 500, { leading: true }),
+  );
+
+  expect(result.current[0]).toBe(initialValue);
+  act(() => {
+    result.current[1]("world");
+  });
+  expect(result.current[0]).toBe("world");
+
+  act(() => {
+    vi.runAllTimers();
+  });
+});

src/hooks/useDebouncedValue.ts

@@ -0,0 +1,51 @@
+import { useEffect, useMemo, useRef, useState } from "react";
+import { useDebouncedCallback } from "./useDebouncedCallback";
+
+type DebounceOptions = {
+  /**
+   * If `leading`, and another callback is not pending, the value will be called immediately,
+   * @default false
+   */
+  leading?: boolean;
+  /**
+   * If `trailing`, the value will be updated after the wait period
+   * @default true
+   */
+  trailing?: boolean;
+};
+
+/**
+ * Debounce the update of a value
+ * @param initialValue The initial value of the debounced value
+ * @param wait Wait period after function hasn't been called for
+ * @param options {DebounceOptions} Options for the debounced callback
+ * @returns Array with the debounced value and a function to update the debounced value
+ *
+ * ```tsx
+ *  const [value, setValue] = useDebouncedValue('hello', 500);
+ *
+ *  setValue('world'); // Will only update the value to 'world' after 500ms
+ *  ```
+ */
+export function useDebouncedValue<T>(
+  initialValue: T,
+  wait: number,
+  options: DebounceOptions = { trailing: true },
+): [T, (value: T) => void] {
+  const [debouncedValue, setDebouncedValue] = useState<T>(initialValue);
+  const previousValueRef = useRef<T | undefined>(initialValue);
+
+  const updateDebouncedValue = useDebouncedCallback(
+    setDebouncedValue,
+    wait,
+    options,
+  );
+
+  // Update the debounced value if the initial value changes
+  if (previousValueRef.current !== initialValue) {
+    updateDebouncedValue(initialValue);
+    previousValueRef.current = initialValue;
+  }
+
+  return [debouncedValue, updateDebouncedValue];
+}