Automatically Count Articles in Docusaurus Sidebar

Docusaurus provides a very feature-rich Sidebar by default, but sometimes it doesn't fit all our needs.

Let's tweak it a bit this time.

The goal is simple. The original Sidebar displays the categories we've specified. When the site starts, it looks for the _category_.json in each directory level, which contains something like this:

{
  "label": "Classic CNNs",
  "link": {
    "type": "generated-index"
  }
}

This would display:

• Classic CNNs
• ... (other categories)

What I'd like to do is count the number of items under each folder and display it directly on the page, like this:

• Classic CNNs (8)
• ... (other categories)

---

Can we just add the count directly in the _category_.json file?

{
  "label": "Classic CNNs (8)",
  "link": {
    "type": "generated-index"
  }
}

And manually update the count every time we add an article?

Absolutely not! We can't write code like that.

Reference Material

To solve this issue, as usual, let's first check Docusaurus' official documentation:

• Docusaurus Sidebar

---

The default Sidebar is autogenerated through the autogenerated option:

/**
 * Creating a sidebar enables you to:
 - create an ordered group of docs
 - render a sidebar for each doc of that group
 - provide next/previous navigation

 The sidebars can be generated from the filesystem, or explicitly defined here.

 Create as many sidebars as you want.
 */

// @ts-check

/** @type {import('@docusaurus/plugin-content-docs').SidebarsConfig} */
const sidebars = {
  // By default, Docusaurus generates a sidebar from the docs folder structure
  tutorialSidebar: [{ type: "autogenerated", dirName: "." }],

  // But you can create a sidebar manually
  /*
  tutorialSidebar: [
    'intro',
    'hello',
    {
      type: 'category',
      label: 'Tutorial',
      items: ['tutorial-basics/create-a-document'],
    },
  ],
   */
};

export default sidebars;

---

After reviewing it, it seems there is no built-in feature that fits our needs. Let's build one ourselves.

Implementation

I'll include comments directly in the code. Here are a few places to note where modifications may be required based on your setup:

1. Line 8: const baseDir = path.join(__dirname, "papers");

   The papers here refers to our folder name. Ensure your directory path is correct.

---

2. Line 20: sidebarItems.push("intro");

   The intro here refers to the name of our homepage. Ensure your homepage name is correct. If there's no homepage, you can remove this line.

---

3. Line 72: return stat.isDirectory() || (stat.isFile() && item.endsWith(".md"));

   Here, .md is the format of our articles. Adjust it based on your format.

---

Here's the implementation. You can see the result directly on the webpage: Papers.

/sidebars.js

const fs = require("fs"); // Import Node.js file system module to work with files and directories
const path = require("path"); // Import Node.js path module to handle file paths

/** @type {import('@docusaurus/plugin-content-docs').SidebarsConfig} */
// This is a type definition for Docusaurus sidebar configuration to enable IDE autocompletion
function generateSidebar() {
  // Set the base directory path, pointing to the 'papers' folder. Modify as needed.
  const baseDir = path.join(__dirname, "papers");

  // Read all subdirectories under 'papers', filtering out hidden ones (starting with a dot)
  const categories = fs.readdirSync(baseDir).filter((item) => {
    const itemPath = path.join(baseDir, item);
    // Ensure it's a directory and not hidden
    return fs.statSync(itemPath).isDirectory() && !item.startsWith(".");
  });

  const sidebarItems = []; // Array to store sidebar items

  // Add a fixed 'intro' item at the beginning
  sidebarItems.push("intro");

  // Iterate through all category directories
  categories.forEach((category) => {
    const categoryPath = path.join(baseDir, category); // Get the full path for each category
    const count = countItemsInDirectory(categoryPath); // Count the number of items in the directory

    // Try to read the '_category_.json' file within the category directory to get label and link
    const categoryJsonPath = path.join(categoryPath, "_category_.json");
    let label = category; // Default label is the directory name
    let link = undefined; // Default link is undefined
    if (fs.existsSync(categoryJsonPath)) {
      // If the '_category_.json' file exists
      const categoryJson = JSON.parse(
        fs.readFileSync(categoryJsonPath, "utf8")
      ); // Read and parse the JSON file
      label = categoryJson.label || category; // Use the label from the JSON file or default to directory name
      link = categoryJson.link; // Use the link from the JSON file
    }

    // Append the item count to the label
    label = `${label} (${count})`;

    // Create a sidebar item, with type 'category', indicating this is a category
    const sidebarItem = {
      type: "category",
      label: label, // Display label
      items: [{ type: "autogenerated", dirName: category }], // Automatically generate document items under the category
    };

    if (link) {
      // If a link is provided, add it to the category
      sidebarItem.link = link;
    }

    sidebarItems.push(sidebarItem); // Add the category item to the sidebar array
  });

  // Return an object containing the sidebar configuration
  return {
    papersSidebar: sidebarItems,
  };
}

// Count the valid items (including subdirectories and Markdown files) in a specified directory
function countItemsInDirectory(dirPath) {
  const items = fs.readdirSync(dirPath).filter((item) => {
    const itemPath = path.join(dirPath, item);
    // Exclude '_category_.json' and hidden files (starting with a dot)
    if (item === "_category_.json" || item.startsWith(".")) return false;
    const stat = fs.statSync(itemPath);
    // Only count directories and .md files
    return stat.isDirectory() || (stat.isFile() && item.endsWith(".md"));
  });
  return items.length; // Return the count of items
}

// Export the generated sidebar configuration for Docusaurus to use
export default generateSidebar();