How to increment the pageIndex in useSWRInfinite hooks?

[realyukii]

i try to implement infinite scroll from the example in docs using useSWRInfinite hooks, here's the code:

import { useEffect } from "react";
import useSWRInfinite from "swr/infinite";

export default function useRecommendation() {
  const { data, error, isLoading, size, setSize } = useSWRInfinite(
    (pageIndex, prevPageData) => {
      if (prevPageData && !prevPageData.length) return null;
      return `/api/recommend?ps=${pageIndex + 1}`;
    },
    (...args) => fetch(...args).then((res) => res.json())
  );
  const onScroll = () => {
    const { scrollTop, scrollHeight, clientHeight } = document.documentElement;
    if (Math.abs(scrollHeight - scrollTop - clientHeight) < 1) {
      setSize(size + 1);
    }
  };

  useEffect(() => {
    window.addEventListener("scroll", onScroll);
    return () => {
      window.removeEventListener("scroll", onScroll);
    };
  }, []);

  if (error) return <div>failed to load</div>;
  if (isLoading) return <div>loading...</div>;
  console.log(data);

  return {
    data,
    error,
    isLoading,
  };
}

in the code above i use pageIndex + 1 cuz the index is start from 1 not zero, but the problem is the pageIndex doesn't incremented once setSize is called, am i missing something important step?

[realyukii]

and one more question, is automatic refetch/revalidation at intervals using useSWRInfinite an expected behavior?