feat: add debounce (#47)

Author: d-koppenhagen

blog/2025-10-signal-forms-part2/README.md

@@ -3,7 +3,7 @@ title: 'Angular Signal Forms Part 2: Advanced Validation and Schema Patterns'
 author: Danny Koppenhagen and Ferdinand Malcher
 mail: dannyferdigravatar@fmalcher.de # Gravatar
 published: 2025-10-15
-lastModified: 2025-11-13
+lastModified: 2025-11-15
 keywords:
   - Angular
   - Signals
@@ -405,6 +405,30 @@ We can use this state to provide user feedback in the UI:
 <!-- ... -->
 ```
 
+## Debounce: Delay updates from the UI
+
+Async validation can be expensive: by default, an async call is made with every character entered in an input field.
+
+The `debounce()` function delays updates from the UI to the form model.
+When applied, updates are only emitted to the form after typing has stopped for the given time (here 500 ms), or when the field loses focus.
+This means that not each and every character changes the form value and triggers validation, but only when the user has paused typing for 500 ms.
+
+```typescript
+import { /* ... */, validateAsync, debounce } from '@angular/forms/signals';
+
+export const registrationSchema = schema<RegisterFormData>((schemaPath) => {
+  // Delay username updates by 500ms
+  debounce(schemaPath.username, 500);
+
+  // Async validation will only trigger after debounce delay
+  validateAsync(schemaPath.username, {
+    // ...
+  });
+});
+```
+
+This prevents excessive API calls during typing and improves performance by batching rapid user input changes.
+
 ## Controlling Field State
 
 Signal Forms also provide functions to control field behavior beyond validation.