This is a library for declarative use of Intersection Observer API with Angular.
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
Create IntersectionObserver with waIntersectionObserver
directive
Observe elements with waIntersectionObservee
directive
Optional: provide root element with waIntersectionRoot
directive and use waIntersectionThreshold
and waIntersectionRootMargin
attributes to configure IntersectionObserver options
NOTE: 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…
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>
Alternatively you can use Observable
-based services:
IntersectionObserveeService
can be used to observe elements under waIntersectionObserver
directive in the DI tree
IntersectionObserverService
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 MyComponent {
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
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15+ | 55+ | 51+ | 12.2+ |
You can use polyfill to support older browsers
You can try online demo here
Other Web APIs for Angular by @ng-web-apis
Do you also want to open-source something, but hate the collateral work? Check out this Angular Open-source Library Starter we’ve created for our projects. It got you covered on continuous integration, pre-commit checks, linting, versioning + changelog, code coverage and all that jazz.
Author: ng-web-apis
Live Demo: https://ng-web-apis.github.io/intersection-observer/
GitHub: https://github.com/ng-web-apis/intersection-observer
#angular #javascript #angularjs