dataroom/lib/utils/use-at-bottom.ts

import * as React from "react";

export function useAtBottom(offset = 0) {
  const [isAtBottom, setIsAtBottom] = React.useState(false);

  React.useEffect(() => {
    const handleScroll = () => {
      setIsAtBottom(
        window.innerHeight + window.scrollY >=
          document.body.offsetHeight - offset,
      );
    };

    window.addEventListener("scroll", handleScroll, { passive: true });
    handleScroll();

    return () => {
      window.removeEventListener("scroll", handleScroll);
    };
  }, [offset]);

  return isAtBottom;
}