Guides / Math
This guide explores how to support math (LaTeX) in MDX. MDX supports standard markdown syntax (CommonMark). That means math is not supported by default. Math can be enabled by using a remark plugin: remark-math
, combined with a rehype plugin: either rehype-katex
(KaTeX) or rehype-mathjax
(MathJax). Like other remark and rehype plugins, they can be passed in remarkPlugins
and rehypePlugins
, respectively, in ProcessorOptions
. More info on plugins is available in § Extending MDX
Say we have an MDX file like this:
# $$\sqrt{a^2 + b^2}$$
The above MDX with math can be transformed with the following module:
import fs from 'node:fs/promises'
import {compile} from '@mdx-js/mdx'
import rehypeKatex from 'rehype-katex'
import remarkMath from 'remark-math'
console.log(
String(
await compile(await fs.readFile('example.mdx'), {
rehypePlugins: [rehypeKatex],
remarkPlugins: [remarkMath]
})
)
)
(alias) module "node:fs/promises"
import fs
(alias) function compile(vfileCompatible: Readonly<Compatible>, compileOptions?: Readonly<CompileOptions> | null | undefined): Promise<VFile>
import compile
Compile MDX to JS.
(alias) function rehypeKatex(options?: Readonly<Options> | null | undefined): (tree: Root, file: VFile) => undefined
import rehypeKatex
Render elements with a language-math
(or math-display
, math-inline
) class with KaTeX.
(alias) function remarkMath(options?: Readonly<Options> | null | undefined): undefined
import remarkMath
Add support for math.
namespace console
var console: Console
The console
module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.
The module exports two specific components:
Console
class with methods such as console.log()
, console.error()
and console.warn()
that can be used to write to any Node.js stream.console
instance configured to write to process.stdout
and process.stderr
. The global console
can be used without calling require('console')
.Warning: The global console object's methods are neither consistently synchronous like the browser APIs they resemble, nor are they consistently asynchronous like all other Node.js streams. See the note on process I/O
for more information.
Example using the global console
:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console
class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
(method) Console.log(message?: any, ...optionalParams: any[]): void
Prints to stdout
with newline. Multiple arguments can be passed, with the first used as the primary message and all additional used as substitution values similar to printf(3)
(the arguments are all passed to util.format()
).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format()
for more information.
var String: StringConstructor
(value?: any) => string
Allows manipulation and formatting of text strings and determination and location of substrings within strings.
(alias) compile(vfileCompatible: Readonly<Compatible>, compileOptions?: Readonly<CompileOptions> | null | undefined): Promise<VFile>
import compile
Compile MDX to JS.
(alias) module "node:fs/promises"
import fs
function readFile(path: PathLike | fs.FileHandle, options?: ({
encoding?: null | undefined;
flag?: OpenMode | undefined;
} & EventEmitter<T extends EventMap<T> = DefaultEventMap>.Abortable) | null): Promise<Buffer> (+2 overloads)
Asynchronously reads the entire contents of a file.
If no encoding is specified (using options.encoding
), the data is returned as a Buffer
object. Otherwise, the data will be a string.
If options
is a string, then it specifies the encoding.
When the path
is a directory, the behavior of fsPromises.readFile()
is platform-specific. On macOS, Linux, and Windows, the promise will be rejected with an error. On FreeBSD, a representation of the directory's contents will be returned.
An example of reading a package.json
file located in the same directory of the running code:
import { readFile } from 'node:fs/promises';
try {
const filePath = new URL('./package.json', import.meta.url);
const contents = await readFile(filePath, { encoding: 'utf8' });
console.log(contents);
} catch (err) {
console.error(err.message);
}
It is possible to abort an ongoing readFile
using an AbortSignal
. If a request is aborted the promise returned is rejected with an AbortError
:
import { readFile } from 'node:fs/promises';
try {
const controller = new AbortController();
const { signal } = controller;
const promise = readFile(fileName, { signal });
// Abort the request before the promise settles.
controller.abort();
await promise;
} catch (err) {
// When a request is aborted - err is an AbortError
console.error(err);
}
Aborting an ongoing request does not abort individual operating system requests but rather the internal buffering fs.readFile
performs.
Any specified FileHandle
has to support reading.
FileHandle
(property) rehypePlugins?: PluggableList | null | undefined
List of rehype plugins (optional).
(alias) function rehypeKatex(options?: Readonly<Options> | null | undefined): (tree: Root, file: VFile) => undefined
import rehypeKatex
Render elements with a language-math
(or math-display
, math-inline
) class with KaTeX.
(property) remarkPlugins?: PluggableList | null | undefined
List of remark plugins (optional).
(alias) function remarkMath(options?: Readonly<Options> | null | undefined): undefined
import remarkMath
Add support for math.
<>
<h1>
<span className="katex">
<span className="katex-mathml">
<math xmlns="http://www.w3.org/1998/Math/MathML">…</math>
</span>
<span className="katex-html" aria-hidden="true">
…
</span>
</span>
</h1>
</>
Important: if you chose rehype-katex
, you should also use katex.css
somewhere on the page to style math properly. At the time of writing, the last version is:
<!-- Get the latest one from: https://katex.org/docs/browser -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.10/dist/katex.min.css" integrity="sha384-wcIxkf4k558AjM3Yz3BBFQUbk/zgIYC2R0QpeeYb+TwlBVMrlgLqwRjRtGZiK7ww" crossorigin="anonymous">
To get the latest link to the stylesheet, go to katex docs
.
Note: see also remark-mdx-math-enhanced
, which you can use to support JavaScript expressions inside of math (such as to access properties or to make calculations)