Add debounce state check function

index.d.ts

@@ -10,6 +10,7 @@ The returned function has the following methods:
 - `.clear()` cancels any scheduled executions.
 - `.flush()` if an execution is scheduled then it will be immediately executed and the timer will be cleared.
 - `.trigger()` executes the function immediately and clears the timer if it was previously set.
+- `.isDebouncing()` checks if the debounce delay is still active.
 */
 declare function debounce<F extends AnyFunction>(
 	function_: F,
@@ -23,6 +24,7 @@ declare namespace debounce {
 		clear(): void;
 		flush(): void;
 		trigger(): void;
+		isDebouncing(): boolean;
 	};
 }
 

index.js

@@ -88,6 +88,8 @@ function debounce(function_, wait = 100, options = {}) {
 		debounced.clear();
 	};
 
+	debounced.isDebouncing = () => Boolean(timeoutId);
+
 	return debounced;
 }
 

readme.md

@@ -41,6 +41,12 @@ To execute immediately and reset the timer if it was previously set:
 window.onresize.trigger();
 ```
 
+To checks if the debounce delay is still active:
+
+```js
+window.onresize.isDebouncing();
+```
+
 ## API
 
 ### debounce(fn, wait, options?)
@@ -54,6 +60,7 @@ The returned function has the following methods:
 - `.clear()` cancels any scheduled executions.
 - `.flush()` if an execution is scheduled then it will be immediately executed and the timer will be cleared.
 - `.trigger()` executes the function immediately and clears the timer if it was previously set.
+- `.isDebouncing()` checks if the debounce delay is still active.
 
 ## Related
 

test.js

@@ -449,3 +449,15 @@ test('calling the trigger should not affect future function calls', async () =>
 
 	clock.restore();
 });
+
+test('should correctly handle debounce state transitions', async () => {
+	const callback = sinon.spy();
+	const fn = debounce(callback, 100);
+	assert.strictEqual(fn.isDebouncing(), false, 'Callback should return false for first execution');
+
+	fn();
+	assert.strictEqual(fn.isDebouncing(), true, 'Callback should return true within debounce delay');
+
+	fn.trigger();
+	assert.strictEqual(fn.isDebouncing(), false, 'Callback should return false after debounce triggered');
+});