umami/components/StickyHeader.js
2020-08-05 19:04:02 -07:00

50 lines
1.1 KiB
JavaScript

import React, { useState, useRef, useEffect } from 'react';
import classNames from 'classnames';
export default function StickyHeader({
className,
stickyClassName,
stickyStyle,
children,
enabled = true,
}) {
const [sticky, setSticky] = useState(false);
const ref = useRef();
const offsetTop = useRef(0);
useEffect(() => {
const checkPosition = () => {
if (ref.current) {
if (!offsetTop.current) {
offsetTop.current = ref.current.offsetTop;
}
const state = window.pageYOffset > offsetTop.current;
if (sticky !== state) {
setSticky(state);
}
}
};
checkPosition();
if (enabled) {
window.addEventListener('scroll', checkPosition);
}
return () => {
window.removeEventListener('scroll', checkPosition);
};
}, [sticky, enabled]);
return (
<div
ref={ref}
data-sticky={sticky}
className={classNames(className, { [stickyClassName]: sticky })}
style={sticky ? { ...stickyStyle, width: ref?.current?.clientWidth } : null}
>
{children}
</div>
);
}