@ng-web-apis/intersection-observer
v4.11.1
Published
A library for declarative use of Intersection Observer API with Angular
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Intersection Observer API for Angular
This is a library for declarative use of Intersection Observer API with Angular.
Install
If you do not have @ng-web-apis/common:
npm i @ng-web-apis/common
Now install the package:
npm i @ng-web-apis/intersection-observer
Usage
Import
IntersectionObserverModule
for directives to workCreate IntersectionObserver with
waIntersectionObserver
directiveObserve elements with
waIntersectionObservee
directiveOptional: provide root element with
waIntersectionRoot
directive and usewaIntersectionThreshold
andwaIntersectionRootMargin
attributes to configure IntersectionObserver optionsNOTE: Keep in mind these are used one time in constructor so you cannot use binding, only strings. Pass comma separated numbers to set an array of thresholds.
Examples
Observing multiple elements intersecting with viewport using single observer
<section
waIntersectionObserver
waIntersectionThreshold="0.5"
>
<div (waIntersectionObservee)="onIntersection($event)">I'm being observed</div>
<div (waIntersectionObservee)="onIntersection($event)">I'm being observed</div>
</section>
Observing elements intersecting with parent element, each having different configuration therefore using individual observers:
<section waIntersectionRoot>
<div
waIntersectionObserver
waIntersectionThreshold="0.5"
(waIntersectionObservee)="onIntersection($event)"
>
I'm being observed
</div>
<div
waIntersectionObserver
waIntersectionThreshold="1,0.5,0"
(waIntersectionObservee)="onIntersection($event)"
>
I'm being observed
</div>
</section>
Services
Alternatively you can use Observable
-based services:
IntersectionObserveeService
can be used to observe elements underwaIntersectionObserver
directive in the DI treeIntersectionObserverService
can be used to observe single element independently. Provide tokens manually to configure it:
@Component({
selector: 'my-component',
providers: [
IntersectionObserverService,
{
provide: INTERSECTION_THRESHOLD,
useValue: 0.5,
},
{
provide: INTERSECTION_ROOT_MARGIN,
useValue: '10px',
},
],
})
export class Example {
constructor(@Inject(IntersectionObserverService) entries$: IntersectionObserverService) {
entries$.subscribe((entries) => {
// Don't forget to unsubscribe
console.log(entries);
});
}
}
In this case provide
INTERSECTION_ROOT
up the DI tree if you want to observe intersection with a particular parent element
Browser support
| | | | | | :-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: | | 15+ | 55+ | 51+ | 12.2+ |
You can use polyfill to support older browsers
Angular Universal
If you want to use this package with SSR, you need to mock IntersectionObserver
class on the server. You can use our
Universal package for this, see
this example.
Demo
You can try online demo here
See also
Other Web APIs for Angular by @ng-web-apis