31 lines
843 B
TypeScript
31 lines
843 B
TypeScript
 
|
import { RefObject, useEffect, useState } from 'react';
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns true once the observed element has come within `margin` pixels of
|
||
|
|
* the viewport. Disconnects the observer after the first intersection so there
|
||
|
|
* is no ongoing overhead.
|
||
|
|
*/
|
||
|
|
export function useNearViewport(ref: RefObject<Element | null>, margin = 200): boolean {
|
||
|
|
const [triggered, setTriggered] = useState(false);
|
||
|
|
|
||
|
|
useEffect(() => {
|
||
|
|
const el = ref.current;
|
||
|
|
if (!el || triggered) return undefined;
|
||
|
|
|
||
|
|
const observer = new IntersectionObserver(
|
||
|
|
(entries) => {
|
||
|
|
if (entries[0]?.isIntersecting) {
|
||
|
|
setTriggered(true);
|
||
|
|
observer.disconnect();
|
||
|
|
}
|
||
|
|
},
|
||
|
|
{ rootMargin: `${margin}px` },
|
||
|
|
);
|
||
|
|
|
||
|
|
observer.observe(el);
|
||
|
|
return () => observer.disconnect();
|
||
|
|
}, [ref, margin, triggered]);
|
||
|
|
|
||
|
|
return triggered;
|
||
|
|
}
|