Adding Slide Numbers to MDX Deck Presentations

MDX Deck is a fast and lightweight library that lets you write presentations in markdown. More specifically, it uses MDX, an extension of markdown that allows you to use JSX and React components. This allows you to do cool things like import React components into your slide deck and interact with them.

First, follow the Getting Started instructions in the README of MDX Deck.

You should end up with the following file structure:

.
├── node_modules
├── deck.mdx
├── README.md
├── package.json
├── package-lock.lock

Then create a <Layout> component:

// layout.js

import React from "react";

const Layout = ({ children }) => {
  return (
    <>
      <div>{children}</div>
      <footer>
        <span>My Awesome Presentation! 🚀</span>
        <span>@corrinachow</span>
      </footer>
    </>
  );
};

export default Layout;

You can now create slides in your deck.mdx file with the Layout component where the slide contents will render as children.

// deck.mdx

import Layout from "./Layout";

<Layout>
  # My Awesome Presentation!
  🚀 Corrina Chow
</Layout>;

This is useful for making headers, footers or layouts for your slides.

Now if you dig into the source code, you'll see that MDX Deck uses a React Context called useDeck to pass deck data between components. This includes the index of the slide, speaker notes, or presentation mode!

This hook happens to be exported from the library and can be used to your advange.

In layout.js file, import the useDeck React hook from mdx-deck. There's a property represents index of the slide you're viewing. From that, you're able to extract slide numbers and add it to your presentation 🥳

// layout.js

import React from "react";
import { useDeck } from "mdx-deck"; // Import useDeck

const Layout = ({ children }) => {
  const state = useDeck(); // Declare a new state variable

  const currentSlide = state.index + 1; // The slides are zero-index
  return (
    <>
      <div>{children}</div>
      <footer>
        <span>My Awesome Presentation! 🚀</span>
        <span>{currentSlide}</span>
        <span>@corrinachow</span>
      </footer>
    </>
  );
};

export default Layout;

There's a bunch of other values that can be accessed with the useDeck context, such as the length of the presentation, or HTML head values.

Hope this was helpful 😄

References

• React Context
• MDX Docs
• MDX Deck