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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | 7x 7x 241x 241x 241x 241x 241x | import { ref, Ref, onMounted, onUnmounted, watch } from 'vue';
/**
* Sets up a basic IntersectionObserver which attaches to the provided
* template ref when the component is mounted. Returns a boolean ref which
* will update to match the current intersection status of the targeted
* element (true if the element is in view, false if it's scrolled out of view).
* If IntersectionObserver is not available, the returned ref will always be false.
*
* @param templateRef
* @param observerOptions
* @return boolean ref
*/
export default function useIntersectionObserver(
templateRef: Ref<Element|undefined>,
observerOptions: IntersectionObserverInit
): Ref<boolean> {
const intersectionRef = ref( false );
let mounted = false;
// Exit early if not running in a browser
Iif ( typeof window !== 'object' ) {
return intersectionRef;
}
// Exit early if any of the necessary features are not supported by the
// user's browser.
if ( !(
'IntersectionObserver' in window &&
'IntersectionObserverEntry' in window &&
'intersectionRatio' in window.IntersectionObserverEntry.prototype
) ) {
return intersectionRef;
}
const observer = new window.IntersectionObserver(
( entries: IntersectionObserverEntry[] ) => {
const entry = entries[ 0 ];
Iif ( entry ) {
intersectionRef.value = entry.isIntersecting;
}
},
observerOptions
);
onMounted( () => {
mounted = true;
Iif ( templateRef.value ) {
observer.observe( templateRef.value );
}
} );
onUnmounted( () => {
mounted = false;
observer.disconnect();
} );
// If the templateRef changes to point to a different element, disconnect the observer from the
// old element and observe the new one instead
watch( templateRef, ( newElement ) => {
// Don't try to observe the element before the component has been mounted; doing that leads
// to strange bugs.
Iif ( !mounted ) {
return;
}
observer.disconnect();
// Reset the ref back to false, just like when we initialized it. If newElement is set, the
// observe callback will run and set the ref to true if newElement is visible.
intersectionRef.value = false;
Iif ( newElement ) {
observer.observe( newElement );
}
} );
return intersectionRef;
}
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