How to use the useSWRInfinite hook for paginating data with a custom scroll trigger in Next.js



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To use the useSWRInfinite hook for paginating data with a custom scroll trigger in Next.js, you need to follow these steps:

  1. Install SWR: If you haven't already, install SWR in your Next.js project. You can do this via npm or yarn:

    npm install swr

    or

    csharp
    yarn add swr

  2. Import the Hook: Import the useSWRInfinite hook in your component file.

  3. Implement the Hook: Use the useSWRInfinite hook in your component to fetch paginated data.

  4. Set Up Pagination Logic: Implement logic to fetch additional pages of data as the user scrolls down.

Here's an example of how you can achieve this:

jsx
// Import necessary modules
import useSWRInfinite from 'swr/infinite';
import { useEffect, useState } from 'react';

// Define your fetcher function to fetch data
const fetcher = async (url) => {
  const res = await fetch(url);
  return res.json();
};

// Define your component
const MyComponent = () => {
  // Define a state to track whether more data is available
  const [hasMore, setHasMore] = useState(true);

  // Define the key for SWR
  const getKey = (pageIndex, previousPageData) => {
    // If there are no more pages, return null
    if (previousPageData && !previousPageData.hasMore) return null;
    // Return the URL for the next page
    return `/api/data?page=${pageIndex + 1}`;
  };

  // Fetch data using useSWRInfinite hook
  const { data, error, size, setSize } = useSWRInfinite(getKey, fetcher);

  // Concatenate all pages of data
  const allData = data ? [].concat(...data) : [];

  // Scroll event handler
  const handleScroll = () => {
    // Check if the user has scrolled to the bottom of the page
    if (
      window.innerHeight + document.documentElement.scrollTop ===
      document.documentElement.offsetHeight
    ) {
      // Fetch more data if available
      if (hasMore) {
        setSize(size + 1);
      }
    }
  };

  // Add scroll event listener when component mounts
  useEffect(() => {
    window.addEventListener('scroll', handleScroll);
    return () => {
      window.removeEventListener('scroll', handleScroll);
    };
  }, []);

  // Set hasMore state based on whether there's more data to fetch
  useEffect(() => {
    setHasMore(data && data[data.length - 1]?.hasMore);
  }, [data]);

  if (error) return <div>Error loading data</div>;

  // Render your data
  return (
    <div>
      {allData.map((item) => (
        <div key={item.id}>{/* Render your item */}</div>
      ))}
      {hasMore && <div>Loading more...</div>}
    </div>
  );
};

export default MyComponent;

In this example:

  • We import useSWRInfinite from SWR and useEffect and useState from React.
  • We define a fetcher function to fetch data.
  • We define a component MyComponent that fetches paginated data using the useSWRInfinite hook.
  • We define a getKey function that returns the URL for the next page of data.
  • We implement a scroll event listener to trigger fetching more data when the user scrolls to the bottom of the page.
  • We update the hasMore state based on whether there's more data to fetch.
  • We render the data and a loading indicator if more data is being fetched.

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