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umami/components/helpers/CheckVisible.js
2020-08-07 02:27:12 -07:00

42 lines
976 B
JavaScript

import React, { useState, useRef, useEffect } from 'react';
function isInViewport(element) {
const rect = element.getBoundingClientRect();
return !(
rect.bottom < 0 ||
rect.right < 0 ||
rect.left > window.innerWidth ||
rect.top > window.innerHeight
);
}
export default function CheckVisible({ className, children }) {
const [visible, setVisible] = useState(false);
const ref = useRef();
useEffect(() => {
const checkPosition = () => {
if (ref.current) {
const state = isInViewport(ref.current);
if (state !== visible) {
setVisible(state);
}
}
};
checkPosition();
window.addEventListener('scroll', checkPosition);
return () => {
window.removeEventListener('scroll', checkPosition);
};
}, [visible]);
return (
<div ref={ref} className={className} data-visible={visible}>
{typeof children === 'function' ? children(visible) : children}
</div>
);
}