Angular Event Plugins

@taiga-ui/event-plugins is a tiny (1KB gzip) library for optimizing change detection cycles for performance sensitive events (such as touchmove, scroll, drag etc.) and declarative preventDefault() and stopPropagation().

How to use

1. Add NG_EVENT_PLUGINS to your app providers:

   bootstrapApplication(AppComponent, {
     providers: [NG_EVENT_PLUGINS],
   });

2. Use new modifiers for events in templates and in @HostListener:

   • .stop to call stopPropagation() on event
   • .prevent to call preventDefault() on event
   • .self to skip bubbled events
   • .silent to call event handler outside Angular's NgZone
   • .capture to listen to events in capture phase
   • .passive to add passive event listener
   • .once to remove event listener after first callback
   • resize to watch for elements changing dimensions with ResizeObserver

   For example:

   <div (mousedown.prevent)="onMouseDown()">Clicking on this DIV will not move focus</div>

   <div (click.stop)="onClick()">Clicks on this DIV will not bubble up</div>

   <div (mousemove.silent)="onMouseMove()">Callbacks to mousemove will not trigger change detection</div>

   <div (click.capture.stop)="onClick()">
     <div (click)="never()">Clicks will be stopped before reaching this DIV</div>
   </div>

3. You can also re-enter NgZone and trigger change detection, using @shouldCall decorator that takes a predicate function as argument:

<div (scroll.silent)="onScroll($event.currentTarget)">
  Scrolling this DIV will only trigger change detection and onScroll callback if it is scrolled to bottom
</div>

import {shouldCall} from '@taiga-ui/event-plugins';

export function scrollFilter({
 scrollTop, scrollHeight, clientHeight
}: HTMLElement): boolean {
    return scrollTop === scrollHeight - clientHeight;
}

// ...

@shouldCall(scrollFilter)
onScroll(_element: HTMLElement): void {
    this.someService.requestMoreData();
}

4. Angular global events only support body, window and document. You can listen to events on any global object with these plugins by replacing : with > symbol, for example:

@HostListener('visualViewport>resize', ['$event.target'])
onPinchZoom({ scale }: VisualViewport) {
    console.log(scale)
}

All examples above work the same when used with @HostListener and CustomEvent

Important notes

• Predicate is called with the same arguments as the decorated method and in the context of class instance (has access to this)

• Decorated method will be called and change detection triggered if predicate returns true.

• .silent modifier will not work with built-in keyboard pseudo-events, such as keydown.enter or keydown.arrowDown since Angular re-enters NgZone inside internal handlers.

Demo

You can try this interactive demo

You can also read this detailed article explaining how this library works

Maintained

@taiga-ui/event-plugins is a part of Taiga UI libraries family which is backed and used by a large enterprise. This means you can rely on timely support and continuous development.

License

🆓 Feel free to use our library in your commercial and private applications

All @taiga-ui/event-plugins packages are covered by Apache 2.0

Read more about this license here