feat(curry): add isPending method to debounce function (#294)

cdn/radash.esm.js

@@ -534,11 +534,15 @@ const debounce = ({ delay }, func) => {
       clearTimeout(timer);
       timer = setTimeout(() => {
         active && func(...args);
+        timer = void 0;
       }, delay);
     } else {
       func(...args);
     }
   };
+  debounced.isPending = () => {
+    return timer !== void 0;
+  };
   debounced.cancel = () => {
     active = false;
   };

cdn/radash.js

@@ -537,11 +537,15 @@ var radash = (function (exports) {
         clearTimeout(timer);
         timer = setTimeout(() => {
           active && func(...args);
+          timer = void 0;
         }, delay);
       } else {
         func(...args);
       }
     };
+    debounced.isPending = () => {
+      return timer !== void 0;
+    };
     debounced.cancel = () => {
       active = false;
     };

docs/curry/debounce.mdx

@@ -21,21 +21,21 @@ const makeSearchRequest = (event) => {
 input.addEventListener('change', debounce({ delay: 100 }, makeSearchRequest))
 ```
 
-## Timming
+## Timing
 
 A visual of the debounce behavior when `delay` is `100`. The debounce function
 returned by `debounce` can be called every millisecond but it will only call
 the given callback after `delay` milliseconds have passed.
 
 ```sh
-                Time: 0ms - - - - 100ms - - - - 200ms - - - - 300ms - - - - 400ms - - - - 
+                Time: 0ms - - - - 100ms - - - - 200ms - - - - 300ms - - - - 400ms - - - -
 debounce Invocations: x x x x - - - - - - - - x x x x x x x x x x - - - - - - - - - - - -
   Source Invocations: - - - - - - - - - - x - - - - - - - - - - - - - - - - - x - - - - -
 ```
 
 ### Cancel
 
-The function returned by `debounce` has a `cancel` property, a function that when called will permanently stop the source function from being debounced.
+The function returned by `debounce` has a `cancel` method that when called will permanently stop the source function from being debounced.
 
 ```ts
 const debounced = debounce({ delay: 100 }, api.feed.refresh)
@@ -47,7 +47,7 @@ debounced.cancel()
 
 ### Flush
 
-The function returned by `debounce` has a `flush` property, a function that when called will directly invoke the source function.
+The function returned by `debounce` has a `flush` method that when called will directly invoke the source function.
 
 ```ts
 const debounced = debounce({ delay: 100 }, api.feed.refresh)
@@ -57,3 +57,15 @@ const debounced = debounce({ delay: 100 }, api.feed.refresh)
 debounced.flush(event)
 ```
 
+### isPending
+
+The function returned by `debounce` has a `isPending` method that when called will return if there is any pending invocation the source function.
+
+```ts
+const debounced = debounce({ delay: 100 }, api.feed.refresh)
+
+// ... sometime later
+
+debounced.isPending()
+```
+

src/curry.ts

@@ -101,6 +101,10 @@ export type DebounceFunction<TArgs extends any[]> = {
    * Cancels the debounced function
    */
   cancel(): void
+  /**
+   * Checks if there is any invocation debounced
+   */
+  isPending(): boolean
   /**
    * Runs the debounced function immediately
    */
@@ -136,11 +140,15 @@ export const debounce = <TArgs extends any[]>(
       clearTimeout(timer)
       timer = setTimeout(() => {
         active && func(...args)
+        timer = undefined
       }, delay)
     } else {
       func(...args)
     }
   }
+  debounced.isPending = () => {
+    return timer !== undefined
+  }
   debounced.cancel = () => {
     active = false
   }

src/tests/curry.test.ts

@@ -190,7 +190,7 @@ describe('curry module', () => {
       expect(mockFunc).toHaveBeenCalledTimes(6)
     })
 
-    test('when we call the flush method it should execute the function immediately', () => {
+    test('executes the function immediately when the flush method is called', () => {
       func.flush()
       expect(mockFunc).toHaveBeenCalledTimes(1)
     })
@@ -208,7 +208,21 @@ describe('curry module', () => {
       expect(mockFunc).toHaveBeenCalledTimes(3)
     })
 
-    test('cancels all pending invocations when cancel is called', async () => {
+    test('cancels all pending invocations when the cancel method is called', async () => {
+      const results: boolean[] = []
+      func()
+      results.push(func.isPending())
+      results.push(func.isPending())
+      await _.sleep(610)
+      results.push(func.isPending())
+      func()
+      results.push(func.isPending())
+      await _.sleep(610)
+      results.push(func.isPending())
+      assert.deepEqual(results, [true, true, false, true, false])
+    })
+
+    test('returns if there is any pending invocation when the pending method is called', async () => {
       func()
       func.cancel()
       await _.sleep(610)