Introduction

Pagination and infinite scrolling significantly improve the user experience of web applications by allowing developers to load large datasets.

Astro.js and Strapi are two powerful tools that developers often use in tandem to create dynamic and efficient web applications.

In this article, you will learn how to enable pagination and infinite scrolling in your Astro.js application using Strapi 5.

Overview of Astro.js and Strapi

Astro.js is a JavaScript framework for building modern, fast, scalable web applications. It provides developers with a clean and organized structure for their code, making it easier to manage and maintain complex projects. Astro.js offers various features and utilities, including routing, state management, and component-based architecture, making it a popular choice among developers for front-end development.

Strapi, on the other hand, is an open-source headless CMS (Content Management System) built with Node.js. It allows developers to quickly and easily create API-driven content management systems. Strapi provides a flexible and customizable content management interface and powerful APIs for managing content, making it an ideal choice for building dynamic web applications.

Importance of Pagination and Infinite Scrolling

Pagination is a technique that helps users work with a large amount of data by dividing it into smaller chunks or pages. It enhances the general user experience by limiting the amount of data loaded at a given time, improving its speed and the time it takes to load.

Infinite scrolling is when content loads as the user scrolls down the page without clicking buttons or links for page navigation. It gives a smooth and engaging browsing experience by loading new content as the user reaches the end of the content displayed. Infinite scrolling is especially effective in applications that contain a massive amount of content and whose volume increases constantly, such as social networks or news portals.

Prerequisites

You will need the following to get started:

• Node.js v18 or later.
• A code editor on your computer.
• Python

Create a Strapi CMS Project

To get started, create a new Strapi 5 backend project by running the command below:

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npx create-strapi-app@rc my-project --quickstart

The above command will scaffold a new Strapi Node.js project and install the required dependencies.

Now, fill out the forms to create your administrator user account.

Create a New Astro App

Next, create a new Astro application by running the command below:

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npm create astro@latest

The above command will prompt you to select where you want to create your new project. Press the ESC key to use the default. Start your project with the Empty template, select no write in Javascript, install dependency, and initialize the new git repository. Overall, your selection should look like the screenshot below:

Creating Strapi Collection Type

To demonstrate how pagination and infinite scrolling work, create a new Article collection, add some entries, and publish them so that the API for your content can be consumed.

The Article collection will have the following data types:

• title: The article's title
• description: The article's description
• content: The article's content

Configure Strapi Collection Type API

To access your Astro application's Article collection API, navigate to Settings > Roles > Public and select the Article collection. In the permissions tab, check to select all to give the public read, write, update, and delete access.

Connecting Astro.js with Strapi CMS

Now, let's connect your Strapi CMS with your Astro app. First, update your astro.config.mjs configuration with the code:

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import { defineConfig } from 'astro/config';

export default defineConfig({
  env: {
    STRAPI_API_URL: process.env.STRAPI_API_URL,
  },
  output: 'hybrid'
});

This configuration:

• Sets up an environment variable STRAPI_API_URL environment variables.
• Specifies the output as "hybrid", indicating that the project will use a hybrid approach combining static and server-rendered content.

Then add STRAPI_API_URL variable to your .env file:

STRAPI_API_URL=http://localhost:1337

Adding sample data for demonstration

With the collection type and Astro configurations created to connect with your Astro app, let's load some sample data to the Articles collection. Create a populate-strapi.js file and add the code:

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import axios from "axios";

const STRAPI_URL = "http://localhost:1337";

async function populateArticles() {
  try {
    const { data: posts } = await axios.get(
      "https://jsonplaceholder.typicode.com/posts"
    );
    for (const post of posts) {
      await axios.post(
        `${STRAPI_URL}/api/articles`,
        {
          data: {
            title: post.title,
            content: post.body,
          },
        },
        {
          headers: {
            "Content-Type": "application/json",
          },
        }
      );
      console.log(`Created article: ${post.title}`);
    }

    console.log("All articles created successfully!");
  } catch (error) {
    console.error("Error:", error.response?.data || error.message);
  }
}

populateArticles();

Here, we defined a populateArticles() to fetch sample data from jsonplaceholder and send a POST request to Strapi CMS to save them in the Article collection.

Run the command below the code in the populateArticles function:

node populate-strapi.js

If everything works as expected, you should see All articles created successfully! printed on your terminal.

Implement Pagination in Astro.js

Now that you've loaded some sample data on your Article collection let's fetch paginated data from Strapi. Create a new pagination.astro file in the pages directory. Then, add the code below to configure the Javascript fetch API to fetch data from your Strapi CMS.

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---
import "../styles/articles.css";

export const prerender = false;
const currentPath = Astro.url.pathname;
const page = parseInt(Astro.url.searchParams.get("page") || "1");
const pageSize = 6;

const fetchArticles = async (page, pageSize) => {
  const response = await fetch(
    `${import.meta.env.STRAPI_API_URL}/api/articles?pagination[page]=${page}&pagination[pageSize]=${pageSize}&populate=*`
  );
  const data = await response.json();
  return data;
};

const { data: articles, meta } = await fetchArticles(page, pageSize);
---

The above code will:

• Set prerender to false, indicating that this page should be server-side rendered.
• Determine the current path and page number from the URL.
• Set a constant pageSize of 6 articles per page.
• Define an asynchronous function fetchArticles that makes a fetch request for articles at the Strapi REST API endpoint. The data returned from this function includes the articles and metadata, such as the current page number and the total number of pages available (meta.pagination.page and meta.pagination.pageCount).
• The URL includes pagination parameters (page and pageSize).
• Uses the STRAPI_API_URL environment variable to construct the full API URL. Requests all populated fields with the populate=* parameter.
• Parses the JSON response and returns the data.
• Call the fetchArticles function with the current page and pageSize.
• Destructure the response to extract the articles data and meta information.

Then render the articles and add buttons to navigate between the articles pages:

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<div class="articles-container">
  <h1>Latest Articles</h1>

  <div class="articles-grid">
    {
      articles.map((article) => (
        <article class="article">
          <h2>{article.title}</h2>
          <div class="article-content" set:html={article.content} />
        </article>
      ))
    }
  </div>

  <nav class="pagination">
    <a
      href={`${currentPath}?page=${meta.pagination.page - 1}`}
      class={`pagination-button ${page <= 1 ? "disabled" : ""}`}
      aria-label="Go to previous page"
      rel={page > 1 ? "prev" : null}
    >
      Previous
    </a>
    <span class="pagination-info">
      Page {page} of {meta.pagination.pageCount}
    </span>
    <a
      href={`${currentPath}?page=${meta.pagination.page + 1}`}
      class={`pagination-button ${page >= meta.pagination.pageCount ? "disabled" : ""}`}
      aria-label="Go to next page"
      rel={page < meta.pagination.pageCount ? "next" : null}
    >
      Next
    </a>
  </nav>
</div>

To add some basic styling to the app, create a styles directory in the root of your project and create an articles.css file. Copy the styles here and add to the articles.css file. Then, on your browser, navigate to /pagination. You can see all the articles displayed on page 6 and navigate between pages by clicking the next and previous page buttons.

Implement Infinite Scrolling in Astro.js

In the previous section, you saw how to add pagination to your Astro application and tested it to see how it improves app load time and user experience. Let's move further to implement infinite scrolling, which helps you achieve the same result of increasing user experience and data load time.

First, the api folder is in the pages directory. In the api directory, create a new articles.js file. This will be where your application will ask for articles it needs from the server. Add the code snippet below:

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export async function GET({ url }) {
  const page = url.searchParams.get("page") || "1";
  const pageSize = url.searchParams.get("pageSize") || "10";

  const response = await fetch(
    `${
      import.meta.env.STRAPI_API_URL
    }/api/articles?pagination[page]=${page}&pagination[pageSize]=${pageSize}&populate=*`
  );
  const data = await response.json();

  return new Response(
    JSON.stringify({
      articles: data.data,
      hasMore: data.meta.pagination.page < data.meta.pagination.pageCount,
      totalPages: data.meta.pagination.pageCount,
    }),
    {
      headers: { "Content-Type": "application/json" },
    }
  );
}

The code snippet sets up an API endpoint to fetch articles from a Strapi server. It defines a GET function to retrieve articles based on pagination parameters like page number and page size. The function sends a request to the Strapi server, receives a list of articles and information about pagination, and checks if there are more pages of articles available. Finally, it formats the list of articles and pagination information and sends it back in a standardized JSON response.

Now, create a new file in your pages directory named infinite-scroll.astro and add the code.

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---
import "../styles/articles.css";

export const prerender = false;

const initialPage = parseInt(Astro.url.searchParams.get("page") || "1");
const pageSize = 10;

const fetchArticles = async (page) => {
  const response = await fetch(
    `${import.meta.env.STRAPI_API_URL}/api/articles?pagination[page]=${page}&pagination[pageSize]=${pageSize}&populate=*`
  );
  const data = await response.json();

  const { data: fetchedArticles, meta } = data;
  return {
    articles: fetchedArticles,
    hasMore: meta.pagination.page < meta.pagination.pageCount,
    totalPages: meta.pagination.pageCount,
  };
};

const {
  articles: initialArticles,
  hasMore: initialHasMore,
  totalPages,
} = await fetchArticles(initialPage);
---                             

The above code loads initial data when the page is first loaded. This ensures the page has some content to display before user interactions occur. Next, add the code below to display the content on the webpage and handle the infinite scrolling functionalities.

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<div class="articles-container">
  <h1>Latest Articles</h1>

  <div class="articles-grid">
    {
      initialArticles.map((article) => (
        <article class="article">
          <h2>{article.title}</h2>
          <div class="article-content" set:html={article.content} />
        </article>
      ))
    }
  </div>

  <div id="article-loader" style="display: none;">Loading more articles...</div>
</div>

<script define:vars={{ initialHasMore, initialPage, pageSize, totalPages }}>
  let isLoading = false;
  let hasMore = initialHasMore;
  let currentPage = initialPage;

  const articleLoader = document.getElementById("article-loader");
  const articlesGrid = document.querySelector(".articles-grid");

  const fetchMoreArticles = async () => {
    if (isLoading || !hasMore) return;

    isLoading = true;
    articleLoader.style.display = "block";

    try {
      const response = await fetch(
        `/api/articles?page=${currentPage + 1}&pageSize=${pageSize}`
      );
      const data = await response.json();

      if (!data.articles || data.articles.length === 0) {
        hasMore = false;
      } else {
        currentPage++;
        data.articles.forEach((article) => {
          const articleElement = document.createElement("article");
          articleElement.className = "article";
          articleElement.innerHTML = `
            <h2>${article.title}</h2>
            <div class="article-content">${article.content}</div>
          `;
          articlesGrid.appendChild(articleElement);
        });
        hasMore = currentPage < totalPages;
      }
      console.log(
        `Fetched page ${currentPage}/${totalPages}, hasMore: ${hasMore}`
      );
    } catch (error) {
      console.error("Error fetching articles:", error);
      hasMore = false;
    } finally {
      isLoading = false;
      articleLoader.style.display = hasMore ? "none" : "block";
      articleLoader.textContent = hasMore
        ? "Loading more articles..."
        : "No more articles to load.";

      if (!hasMore) {
        window.removeEventListener("scroll", handleScroll);
        console.log("No more articles, removed scroll listener");
      }
    }
  };

  const handleScroll = () => {
    if (isLoading || !hasMore) return;

    const scrollHeight = document.documentElement.scrollHeight;
    const scrollTop = window.scrollY || document.documentElement.scrollTop;
    const clientHeight =
      window.innerHeight || document.documentElement.clientHeight;

    if (scrollTop + clientHeight >= scrollHeight - 200) {
      console.log(`Triggering fetch for page ${currentPage + 1}`);
      fetchMoreArticles();
    }
  };

  window.addEventListener("scroll", handleScroll);
</script>                                   

The above code will:

• Create a <div> with the class “articles-container” which includes a <h2> “Latest Articles” and a grid layout for articles.
• Use JavaScript to render the articles obtained from the server in real time.
• Create a variable isLoading, hasMore, currentPage and select necessary elements from the DOM articleLoader, articlesGrid.
• Create a function named fetchMoreArticles, which will load more articles from the server when the user scrolls down the page. Within fetchMoreArticles, to avoid multiple server requests while waiting for a response, we use the isLoading flag, show a loading message (articleLoader), and update the current page number (currentPage).
• Use the fetch API to make a GET request to our API endpoint /api/articles with the current page number and page size as parameters. After getting the response, we add the new articles to the articles grid and set hasMore as true or false, depending on the availability of more articles.
• Create the function handleScroll that will listen for scroll events and call the function fetchMoreArticles when the user scrolls down to the bottom of the page.
• Use the addEventListener method to the window object to trigger the handleScroll function when the user scrolls.

Testing App

Now, navigate to the /infinite-scroll endpoint on your browser to see the infinite scrolling feature in action.

You can find the code for the front end of this tutorial in this GitHub repository. Clone and start the Astro development server by running the command below:

npm run dev

Conclusion

This tutorial has shown you how to enable pagination and infinite scrolling in your Astro application. In this case, we began with a brief of Astro and Strapi CMS before delving into endless scrolling. Then, we went deeper into showing how the Astro application can do pagination and infinite scrolling using Strapi 5.

Pagination and infinite scrolling should be included in any application involving a lot of data, such as a blog, news app, or social media app. The issue here is identifying when to apply each of the two methods. Pagination may be more applicable if you work with many data sets where users usually want to go to a specific page. However, if the aim is to give the users the functionality of browsing through the page and loading more content as they scroll down, then infinite scrolling can be more applicable. Finally, the decision depends on your application's specific requirements and user experience goals.