Angular
Fix ResizeObserver Loop Completed with Undelivered Notifications Error in Angular
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Introduction
Usually in Angular, ResizeObserver loop completed with undelivered notifications error occurs when the ResizeObserver detects size changes but not able to deliver all the callbacks before the next frame rendering. This event happens when there is frequent modification of layout that encounters undefined notification.
Solutions to Resolve
1. Throttle or Debounce Resize Events
Limit the frequency of resize event handling to reduce the number of notifications.
Example using rxjs:
import { debounceTime } from 'rxjs/operators';import { fromEvent } from 'rxjs';ngOnInit() { fromEvent(window, 'resize') .pipe(debounceTime(500)) .subscribe(() => { this.onResize(); // Your resize handling logic });}
This approach minimizes fast event handling by adding a user selected delay in ms between resize event triggers.
2. Avoid Recursive Layout Changes
Ensure layout recalculations in response to resize events do not recursively trigger additional resize events.
Check for common causes:
Direct DOM manipulations affecting layout and size.
Multiple calls to ChangeDetectorRef.detectChanges() within resize event handlers.
3. Use NgZone.runOutsideAngular for Heavy DOM Observations
Move non-critical resize operations outside Angular’s zone to prevent frequent change detection.
Example:
constructor(private ngZone: NgZone) {}ngOnInit() { this.ngZone.runOutsideAngular(() => { const resizeOb = new ResizeObserver(entries => { for (let entry of entries) { console.log('Resized:', entry.contentRect); } }); resizeOb.observe(document.body); });}
This prevents unnecessary Angular re-renders while still observing resize changes.
4. Limit the Number of Observed Elements
ResizeObservers watching too many elements can overload the system and trigger cascading layout shifts. Observe only essential elements to reduce load.
5. Ensure Proper Cleanup
When using ResizeObserver, ensure it is disconnected when the component is destroyed to avoid memory leaks.
Example:
private resizeObserver: ResizeObserver;ngOnInit() { this.resizeObserver = new ResizeObserver(() => { console.log('Resize detected'); }); this.resizeObserver.observe(document.body);}ngOnDestroy() { this.resizeObserver.disconnect();}Important Tips
- Throttle or debounce resize event handling to limit frequency.
- Avoid recursive layout changes within resize handlers.
- Use NgZone.runOutsideAngular to handle non-critical resize events.
- Limit observed elements to reduce notifications.
- Disconnect observers to prevent memory leaks.
Implementing these practices can help resolve the ResizeObserver error and improve the performance of your Angular application.
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