mdx-bundler 🦤

Give me MDX/TSX strings and I'll give you back a string of JS you can eval.

The problem

You have a string of MDX and various TS/JS files that it uses and you want to get a bundled version of these files to eval in the browser.

This solution

Give your MDX and JS strings to this function, and it will give you back a single string of the bundled code.

Installation
Usage
Compilation target
Rollup options
Inspiration
Other Solutions
Issues
- 🐛 Bugs
- 💡 Feature Requests
Contributors ✨
LICENSE

Installation

This module is distributed via npm which is bundled with node and should be installed as one of your project's dependencies:

npm install --save mdx-bundler

Usage

import {bundleMDX} from 'mdx-bundler'

const mdxSource = `
---
title: Example Post
published: 2021-02-13
description: This is some description
---

# Wahoo

import Demo from './demo'

Here's a **neat** demo:

<Demo />
`.trim()

const result = await bundleMDX(mdxSource, {
  files: {
    './demo.tsx': `
import * as React from 'react'

function Demo() {
  return <div>Neat demo!</div>
}

export default Demo
    `,
  },
})

const {code, frontmatter} = result

From there, you send the code to your client, and then:

import * as React from 'react'
import {MDXProvider} from '@mdx-js/react'
import {getMDXComponent} from 'mdx-bundler/client'

function Post({code, frontmatter}) {
  // it's generally a good idea to memoize this function call to
  // avoid re-creating the component every render.
  const Component = React.useMemo(() => getMDXComponent(code), [code])
  return (
    <MDXProvider>
      <header>
        <h1>{frontmatter.title}</h1>
        <p>{frontmatter.description}</p>
      </header>
      <main>
        <Component />
      </main>
    </MDXProvider>
  )
}

Ultimately, this gets rendered (basically):

<header>
  <h1>This is the title</h1>
  <p>This is some description</p>
</header>
<main>
  <div>
    <h1>Wahoo</h1>

    <p>Here's a <strong>neat</strong> demo:</p>

    <div>Neat demo!</div>
  </div>
</main>

Files

The files config is an object of all the files you're bundling. The key is the path to the file (relative to the MDX source) and the value is the string of the file source code. You could get these from the filesystem or from a remote database. If your MDX doesn't reference other files (or only imports things from node_modules), then you can omit this entirely.

Compilation target

We use rollup to bundle your MDX and its dependencies and babel to compile things. We're using @babel/preset-env and you can configure this using the standard browserlist configuration. learn more.

Rollup options

You can customize the rollup configuration used with the rollup options:

const result = await bundleMDX(mdxSource, {
  files: {
    /* ... */
  },
  rollup: {
    getInputOptions,
    getOutputOptions,
  },
})

Each of these is a function that receives the default options and should return the options you want used.

This should allow you to customize the external and global configuration for rollup. For example, if your MDX file uses the d3 library and your app exposes window.d3 you could configure rollup to externalize that and replace all references with the global d3 to avoid double-bundling d3. When you call getMDXComponent, you'll pass d3 as a second argument: getMDXComponent(code, {d3: window.d3}). Here's an example:

// server-side or build-time code that runs in Node:
import {bundleMDX} from 'mdx-bundler'

const mdxSource = `
# This is the title

import leftPad from 'left-pad'

<div>{leftPad("Neat demo!", 12, '!')}</div>
`.trim()

const result = await bundleMDX(mdxSource, {
  // NOTE: this is *only* necessary if you want to share deps between your MDX
  // file bundle and the host app. Otherwise, all deps will just be bundled.
  // So it'll work either way, this is just an optimization to avoid sending
  // multiple copies of the same library to your users.
  rollup: {
    getInputOptions(options) {
      // Tell rollup that `left-pad` should *not* be bundled.
      // By default `options.external` is: ['react', 'react-dom']
      // so we'll add 'left-pad' to tell rollup to not bundle it with our MDX code
      options.external = [...(options.external as Array<string>), 'left-pad']
      return options
    },
    getOutputOptions(options) {
      // Tell rollup that it should replace the left-pad import with a global variable.
      // By default `options.globals` is: {react: 'React', 'react-dom': 'ReactDOM'}
      // so we'll add 'left-pad': 'myLeftPad' to tell it what the global variable name is
      options.globals = {...options.globals, 'left-pad': 'myLeftPad'}
      return options
    },
  },
})

// server-rendered and/or client-side code that can run in the browser or Node:
import * as React from 'react'
import leftPad from 'left-pad'
import {MDXProvider} from '@mdx-js/react'
import {getMDXComponent} from 'mdx-bundler/client'

function MDXPage({code}: {code: string}) {
  const Component = React.useMemo(
    () => getMDXComponent(result.code, {myLeftPad: leftPad}),
    [result.code, leftPad],
  )
  return (
    <main>
      <MDXProvider>
        <Component />
      </MDXProvider>
    </main>
  )
}

Inspiration

As I was rewriting kentcdodds.com to remix, I decided I wanted to keep my blog posts as MDX, but I didn't want to have to compile them all at build time or be required to redeploy every time I fix a typo. So I made this which allows my server to compile on demand.