micromark-extension-math
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!Chatchat-badgechatmicromark extensions to support math (
$C_L$
).Contents
* [`math(options?)`](#mathoptions)
* [`mathHtml(options?)`](#mathhtmloptions)
* [`HtmlOptions`](#htmloptions)
* [`Options`](#options)
What is this?
This package contains two extensions that add support for math syntax in markdown tomicromark
micromark.As there is no spec for math in markdown, this extension follows how code (fenced and text) works in Commonmark, but uses dollars.
When to use this
This project is useful when you want to support math in markdown. Extending markdown with a syntax extension makes the markdown less portable. LaTeX equations are also quite hard. But this mechanism works well when you want authors, that have some LaTeX experience, to be able to embed rich diagrams of math in scientific text.You can use these extensions when you are working with
micromark
micromark
already.When you need a syntax tree, you can combine this package with
mdast-util-math
mdast-util-math.All these packages are used
remark-math
remark-math, which focusses on
making it easier to transform content by abstracting these internals away.Install
This package is ESM onlyesm. In Node.js (version 16+), install with npm:npm install micromark-extension-math
In Deno with [`esm.sh`][esmsh]:
```js
import {math, mathHtml} from 'https://esm.sh/micromark-extension-math@3'
In browsers with
esm.sh
esmsh:<script type="module">
import {math, mathHtml} from 'https://esm.sh/micromark-extension-math@3?bundle'
</script>
Use
Say our documentexample.md
contains:Lift($L$) can be determined by Lift Coefficient ($C_L$) like the following equation.
$$
L = \frac{1}{2} \rho v^2 S C_L
$$
…and our module
example.js
looks as follows:import fs from 'node:fs/promises'
import {micromark} from 'micromark'
import {math, mathHtml} from 'micromark-extension-math'
const output = micromark(await fs.readFile('example.md'), {
extensions: [math()],
htmlExtensions: [mathHtml()]
})
console.log(output)
…now running
node example.js
yields (abbreviated):<p>Lift(<span class="math math-inline"><span class="katex">…</span></span>) can be determined by Lift Coefficient (<span class="math math-inline"><span class="katex">…</span></span>) like the following equation.</p>
<div class="math math-display"><span class="katex-display"><span class="katex">…</span></span></div>
API
This package exports the identifiersmath
api-math and
mathHtml
api-math-html.
There is no default export.The export map supports the
development
conditiondevelopment.
Run node --conditions development module.js
to get instrumented dev code.
Without this condition, production code is loaded.math(options?)
Create an extension for micromark
to enable math syntax.Parameters
options
(Options
api-options, default:{}
)
— configuration
Returns
Extension formicromark
that can be passed in extensions
, to enable math
syntax (Extension
micromark-extension).mathHtml(options?)
Create an extension for micromark
to support math when serializing to HTML.👉 Note: this uses KaTeX to render math.
Parameters
options
(HtmlOptions
api-html-options, default:{}
)
— configuration
Returns
Extension formicromark
that can be passed in htmlExtensions
, to support
math when serializing to HTML (HtmlExtension
micromark-html-extension).HtmlOptions
Configuration for HTML output (optional).👉 Note: passed tokatex.renderToString
katex-options.displayMode
is overwritten by this plugin, tofalse
for math in text (inline), andtrue
for math in flow (block).
Type
type Options = Omit<import('katex').KatexOptions, 'displayMode'>
Options
Configuration (TypeScript type).Fields
singleDollarTextMath
(boolean
, default:true
)
— whether to support math (text, inline) with a single dollar.
Single dollars work in Pandoc and many other places, but often interfere
with “normal” dollars in text.
If you turn this off, you use two or more dollars for text math.
Authoring
When authoring markdown with math, keep in mind that math doesn’t work in most places. Notably, GitHub currently has a really weird crappy client-side regex-based thing. But on your own (math-heavy?) site it can be great! You can use code (fenced) with an info string ofmath
to improve this, as
that works in many places.HTML
Math (flow) does not relate to HTML elements.MathML
, which is sort of like SVG but for math, exists but it doesn’t work
well and isn’t widely supported.
Instead, this uses KaTeX, which generates MathML as a fallback but also
generates a bunch of divs and spans so math look pretty.
The KaTeX result is wrapped in <div>
(for flow, block) and <span>
(for text,
inline) elements, with two classes: math
and either math-display
or
math-inline
.When turning markdown into HTML, each line ending in math (text) is turned into a space.
CSS
The HTML produced by KaTeX requires CSS to render correctly. You should usekatex.css
somewhere on the page where the math is shown to
style it properly.
At the time of writing, the last version is:<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.css">
Syntax
Math forms with the following BNF:; Restriction: the number of markers in the closing sequence must be equal
; to the number of markers in the opening sequence.
math_text ::= sequence_text 1*byte sequence_text
math_flow ::= fence_open *( eol *line ) [ eol fence_close ]
; Restriction: not preceded or followed by the marker.
sequence_text ::= 1*'$'
fence_open ::= sequence_flow meta
; Restriction: the number of markers in the closing fence sequence must be
; equal to or greater than the number of markers in the opening fence
; sequence.
fence_close ::= sequence_flow *space_or_tab
sequence_flow ::= 2*'$'
; Restriction: the marker cannot occur in `meta`
meta ::= 1*line
; Character groups for informational purposes.
byte ::= 0x00..=0xFFFF
eol ::= '\n' | '\r' | '\r\n'
line ::= byte - eol
The above grammar shows that it is not possible to create empty math (text). It is possible to include the sequence marker (dollar) in math (text), by wrapping it in bigger or smaller sequences:
Include more: $a$$b$ or include less: $$a$b$$.
It is also possible to include just one marker:
Include just one: $$ $ $$.
Sequences are “gready”, in that they cannot be preceded or followed by more markers. To illustrate:
Not math: $$x$.
Not math: $x$$.
Escapes work, this is math: \$$x$.
Escapes work, this is math: $x$\$.
Yields:
<p>Not math: $$x$.</p>
<p>Not math: $x$$.</p>
<p>Escapes work, this is math: $<span>…</span>.</p>
<p>Escapes work, this is math: <span>…</span>$.</p>
That is because, when turning markdown into HTML, the first and last space, if both exist and there is also a non-space in the math, are removed. Line endings, at that stage, are considered as spaces.
As the math (flow) construct occurs in flow, like all flow constructs, it must be followed by an eol (line ending) or eof (end of file).
The above grammar does not show how indentation of each line is handled. To parse math (flow), let
x
be the number of space_or_tab
characters
before the opening fence sequence, after interpreting tabs based on how many
virtual spaces they represent.
Each line of text is then allowed (not required) to be indented with up
to x
spaces or tabs, which are then ignored as an indent instead of being
considered as part of the content.
This indent does not affect the closing fence.
It can be indented up to a separate 3 real or virtual spaces.
A bigger indent makes it part of the content instead of a fence.The
meta
part is interpreted as the stringmicromark-content-types content
type.
That means that character escapes and character references are allowed.The optional
meta
part is ignored: it is not used when parsing or
rendering.Types
This package is fully typed with TypeScript. It exports the additional typesHtmlOptions
api-html-options
and Options
api-options.Compatibility
Projects maintained by the unified collective are compatible with maintained versions of Node.js.When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line,
micromark-extension-math@^3
, compatible with Node.js 16.This package works with
micromark
version 3
and later.Security
This package is safe assuming that you trust KaTeX. Any vulnerability in it could open you to a cross-site scripting (XSS)xss attack.Related
— remark (and rehype) plugins to support math
— mdast utility to support math
Contribute
Seecontributing.md
in micromark/.github
contributing for ways to get
started.
See support.md
support for ways to get help.This project has a code of conductcoc. By interacting with this repository, organization, or community you agree to abide by its terms.