This is a library for optimizing performance sensitive events and declarative preventDefault and stopPropagation
npm install @tinkoff/ng-event-pluginsEventPluginsModule to your app module:
typescript
import {NgModule} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';
import {EventPluginsModule} from '@tinkoff/ng-event-plugins'; // <-- THIS
@NgModule({
bootstrap: [
/.../
],
imports: [
/.../
BrowserModule,
EventPluginsModule, // <-- GOES HERE
],
declarations: [
/.../
],
})
export class AppModule {}
`
> BrowserModule or BrowserAnimationsModule must go first. You will see a warning if you mess the order.
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
For example:
`html
Clicking on this DIV will not move focus
`
`html
Clicks on this DIV will not bubble up
`
`html
Callbacks to mousemove will not trigger change detection
`
`html
Clicks will be stopped before reaching this DIV
`
3. You can also re-enter NgZone and trigger change detection, using @shouldCall decorator that takes a predicate
function as argument:
`html
Scrolling this DIV will only trigger change detection and onScroll callback if it is scrolled to bottom
`
`typescript
import {shouldCall} from '@tinkoff/ng-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:
`ts
@HostListener('visualViewport>resize', ['$event.target'])
onPinchZoom({ scale }: VisualViewport) {
console.log(scale)
}
`
> All examples above work the same when used with @HostListener and CustomEvent
$3
- Predicate is called with the same arguments as the decorated method and in the context of class instance (has access
to this)
- Decorated method will be called and change detection triggered if predicate returns true.
- Predicates must be exported named function for AOT, arrow functions will trigger build error.
- .silent modifier will not work with built-in keyboard pseudo-events, such as keydown.enter or keydown.arrowDown
since Angular re-enters NgZone inside internal handlers.
Observable host bindings
In this library there's also a plugin that enables observable host bindings. Sounds weird to do host binding with event
plugin, but the code is actually pretty simple. You can read more about it in
this article.
To use it you need to couple @HostListener and @HostBinding on the same Observable property with following syntax:
`ts
@HostBinding('$.disabled')
@HostListener('$.disabled')
readonly disabled$ = asCallable(this.service.loading$)
`
This supports all the native Angular syntax, such as class.class-name or style.width.px.
IMPORTANT NOTES:
- Until this issue is resolved you would have to use
NO_ERRORS_SCHEMA in your module in order to bind to arbitrary properties
- asCallable is a utility function from this library that simply adds Function to the type so Angular thinks it
could be a host listener
- To bind attributes you need to add .attr modifier in the end, not the beginning like in basic Angular binding. This
is due to Angular using regexp to match for attr. string in @HostBinding decorator:
`ts
@HostBinding('$.aria-label.attr')
@HostListener('$.aria-label.attr')
readonly label$ = asCallable(this.translations.get$('label'));
``