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 is an async function that will compile and bundle your MDX files and their dependencies. It uses esbuild, so it's VERY fast and supports TypeScript files (for the dependencies of your MDX files). It also uses xdm which is a more modern and powerful MDX compiler with fewer bugs and more features (and no extra runtime requirements).
Your source files could be local, in a remote github repo, in a CMS, or wherever
else and it doesn't matter. All mdx-bundler cares about is that you pass it
all the files and source code necessary and it will take care of bundling
everything for you.
"What's so cool about MDX?"
MDX enables you to combine terse markdown syntax for your content with the power of React components. For content-heavy sites, writing the content with straight-up HTML can be annoyingly verbose. Often people solve this using a WSYWIG editor, but too often those fall short in mapping the writer's intent to HTML. Many people prefer using markdown to express their content source and have that parsed into HTML to be rendered.
The problem with using Markdown for your content is if you want to have some
interactivity embedded into your content, you're pretty limited. You either need
to insert an element that JavaScript targets (which is annoyingly indirect), or
you can use an iframe or something.
As previously stated, MDX enables you to combine terse markdown syntax for your content with the power of React components. So you can import a React component and render it within the markdown itself. It's the best of both worlds.
"How is this different from next-mdx-remote?"
mdx-bundler actually bundles dependencies of your MDX files. For example, this
won't work with next-mdx-remote, but it will with mdx-bundler:
---
title: Example Post
published: 2021-02-13
description: This is some description
---
# Wahoo
import Demo from './demo'
Here's a **neat** demo:
<Demo />next-mdx-remote chokes on that import because it's not a bundler, it's just a
compiler. mdx-bundler is an MDX compiler and bundler. That's the difference.
"How is this different from the mdx plugins for webpack or rollup?"
Those tools are intended to be run "at build time" and then you deploy the built version of your files. This means if you have some content in MDX and want to make a typo change, you have to rebuild and redeploy the whole site. This also means that every MDX page you add to your site will increase your build-times, so it doesn't scale all that well.
mdx-bundler can definitely be used at build-time, but it's more powerfully
used as a runtime bundler. A common use case is to have a route for your MDX
content and when that request comes in, you load the MDX content and hand that
off to mdx-bundler for bundling. This means that mdx-bundler is infinitely
scalable. Your build won't be any longer regardless of how much MDX content you
have. Also, mdx-bundler is quite fast, but to make this on-demand bundling
even faster, you can use appropriate cache headers to avoid unnecessary
re-bundling.
Webpack/rollup/etc also require that all your MDX files are on the local filesystem to work. If you want to store your MDX content in a separate repo or CMS, you're kinda out of luck or have to do some build-time gymnastics to get the files in place for the build.
With mdx-bundler, it doesn't matter where your MDX content comes from, you can
bundle files from anywhere, you're just responsible for getting the content into
memory and then you hand that off to mdx-bundler for bundling.
"Does this work with Remix/Gatsby/Next/CRA/etc?"
Totally. It works with any of those tools. Depending on whether your
meta-framework supports server-side rendering, you'll implement it differently.
You might decide to go with a built-time approach (for Gatsby/CRA), but as
mentioned, the true power of mdx-bundler comes in the form of on-demand
bundling. So it's best suited for SSR frameworks like Remix/Next.
"Why the dodo bird emoji? 🦤"
Why not?
"Why does this use XDM instead of @mdx-js?"
It has more features, fewer bugs, and no runtime!
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
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} = resultFrom there, you send the code to your client, and then:
import * as React from '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 (
<>
<header>
<h1>{frontmatter.title}</h1>
<p>{frontmatter.description}</p>
</header>
<main>
<Component />
</main>
</>
)
}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>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.
This allows you to modify the built-in xdm configuration (passed to xdm.compile). This can be helpful for specifying your own remarkPlugins/rehypePlugins.
bundleMDX(mdxString, {
xdmOptions(input, options) {
// this is the recommended way to add custom remark/rehype plugins:
// The syntax might look weird, but it protects you in case we add/remove
// plugins in the future.
options.remarkPlugins = [...(options.remarkPlugins ?? []), myRemarkPlugin]
options.rehypePlugins = [...(options.rehypePlugins ?? []), myRehypePlugin]
return options
},
})You can customize any of esbuild options with the option esbuildOptions. This
takes a function which is passed the default esbuild options and expects an
options object to be returned.
bundleMDX(mdxSource, {
esbuildOptions(options) {
options.minify = false
options.target = [
'es2020',
'chrome58',
'firefox57',
'safari11',
'edge16',
'node12',
]
return options
},
})More information on the available options can be found in the esbuild documentation.
It's recommended to use this feature to configure the target to your desired
output, otherwise, esbuild defaults to esnext which is to say that it doesn't
compile any standardized features so it's possible users of older browsers will
experience errors.
This tells esbuild that a given module is externally available. For example, if
your MDX file uses the d3 library and you're already using the d3 library in
your app then you'll end up shipping d3 to the user twice (once for your app
and once for this MDX component). This is wasteful and you'd be better off just
telling esbuild to not bundle d3 and you can pass it to the component
yourself when you call getMDXComponent.
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.
globals: {'left-pad': 'myLeftPad'},
})// 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 {getMDXComponent} from 'mdx-bundler/client'
function MDXPage({code}: {code: string}) {
const Component = React.useMemo(
() => getMDXComponent(result.code, {myLeftPad: leftPad}),
[result.code, leftPad],
)
return (
<main>
<Component />
</main>
)
}MDX Bundler passes on
XDM's ability to substitute components
through the components prop on the component returned by getMDXComponent.
Here's an example that removes p tags from around images.
import * as React from 'react'
const Paragraph: React.FC = props => {
if (typeof props.children !== 'string' && props.children.type === 'img') {
return <>{props.children}</>
}
return <p {...props} />
}
function MDXPage({code}: {code: string}) {
const Component = React.useMemo(() => getMDXComponent(code), [code])
return (
<main>
<Component components={{p: Paragraph}} />
</main>
)
}esbuild relies on __dirname to work out where is executable is, Next.JS and
Webpack can sometimes break this and esbuild needs to be told manually where to
look.
Adding the following code before your bundleMDX will point esbuild directly at
the correct executable for your platform.
import path from 'path'
if (process.platform === 'win32') {
process.env.ESBUILD_BINARY_PATH = path.join(
process.cwd(),
'node_modules',
'esbuild',
'esbuild.exe',
)
} else {
process.env.ESBUILD_BINARY_PATH = path.join(
process.cwd(),
'node_modules',
'esbuild',
'bin',
'esbuild',
)
}More information on this issue can be found in this article.
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.
There's next-mdx-remote but it's more of an mdx-compiler than a bundler (can't bundle your mdx for dependencies). Also it's focused on Next.js whereas this is meta-framework agnostic.
Looking to contribute? Look for the Good First Issue label.
Please file an issue for bugs, missing documentation, or unexpected behavior.
Please file an issue to suggest new features. Vote on feature requests by adding a 👍. This helps maintainers prioritize what to work on.
Thanks goes to these people (emoji key):
 Kent C. Dodds 💻 📖 🚇 |
 benwis 🐛 👀 |
 Adam Laycock 💻 |
 Titus 🤔 👀 💻 |
 Christian Murphy 🤔 |
This project follows the all-contributors specification. Contributions of any kind welcome!
MIT