lil2-remark-gfm

remark-gfm 4.0.1 rewritten in typed LilScript: GitHub Flavored Markdown (autolink literals, footnotes, strikethrough, tables, task lists) on the flat lil2 pipeline, with the same trees as upstream.

It reimplements what remark-gfm bundles: micromark-extension-gfm (the syntax) and mdast-util-gfm (the mdast handlers and the literal-autolink transform). mdast-util-to-hast handles GFM nodes by default, as upstream does. Inside the family it is compiled into lil2-react-markdown's gfm flavor; on its own it turns markdown into mdast and hast columns.

Integers, not strings

| upstream | lil2-remark-gfm | |---|---| | token types 'table', 'strikethrough', … | ints in the GFM range (TYPES_GFM + n) | | construct names for disable | construct ids (CONSTRUCTS_GFM + n) | | parser.gfmFootnotes (an array of labels) | interned identifier ids with a defined-as-footnote flag | | table.align: ['left', null, …] | an int run (ALIGN_LEFT, ALIGN_NONE, …) the table node points into | | hast align: 'left' | a keyword property value (KW_LEFT) | | footnote and definition lookups by uppercased label | arrays indexed by identifier id |

Install

npm install @itslil/lil2-remark-gfm

TypeScript types are included. One ES module per entry; Node, Deno, Bun and workers get dist/, bundlers targeting browsers get dist/browser/ through the browser condition.

Use

import {fromMarkdown, markdownToHast} from '@itslil/lil2-remark-gfm'
import {ALIGN_CENTER, ALIGN_LEFT, ALIGN_NONE, ALIGN_RIGHT, K_DELETE, K_TABLE} from '@itslil/lil2-remark-gfm/constants'

const tree = fromMarkdown('| name | qty | price |\n|:-----|:---:|------:|\n| tea | 2 | 4.50 |\n\n~~sold out~~', true)
const [kind, , , , , , , num, , , , , , , , aux] = tree

// A table's `num` is the offset of its alignments in `aux`: a count, then one ALIGN_* per column.
const table = kind.indexOf(K_TABLE)
const names = {[ALIGN_NONE]: 'none', [ALIGN_LEFT]: 'left', [ALIGN_CENTER]: 'center', [ALIGN_RIGHT]: 'right'}
const align = aux.slice(num[table] + 1, num[table] + 1 + aux[num[table]]).map(a => names[a as keyof typeof names])
console.log(align) // [ 'left', 'center', 'right' ]
console.log(kind.includes(K_DELETE)) // true

const hast = markdownToHast('- [x] done\n- [ ] next')
console.log(hast[18].includes('input')) // task list checkboxes

fromMarkdown(value, singleTilde?) is remark-parse with remark-gfm (singleTilde defaults to false here; pass true for remark-gfm's default); markdownToHast(value, allowDangerousHtml?) adds remark-rehype. The columns are lil2-mdast-util-from-markdown's and lil2-mdast-util-to-hast's; the constants come from @itslil/lil2-remark-gfm/constants. In React, use @itslil/lil2-react-markdown/gfm.

Which package

| you want | package | |---|---| | React elements | @itslil/lil2-react-markdown (/gfm, /full for GFM, math, KaTeX) | | an HTML string, CommonMark | @itslil/lil2-micromark | | an HTML string with GFM, math or KaTeX | renderToStaticMarkup of lil2-react-markdown's /full flavor (below) | | mdast (syntax tree) | lil2-mdast-util-from-markdown; with GFM lil2-remark-gfm, math lil2-remark-math, breaks lil2-remark-breaks | | elements from hast columns through any JSX runtime | lil2-hast-util-to-jsx-runtime | | hast (HTML tree) | lil2-mdast-util-to-hast and the same three, or lil2-rehype-katex with formulas rendered |

Every package is one self-contained ES module with no runtime dependencies (React and KaTeX aside), ships its TypeScript types, and resolves to a Node build or a browser build through its exports conditions.

Measured (2026-10-04)

The browser build against [email protected] bundled for the browser with esbuild and minified by Terser, esbuild and Oxc (the smallest shown). Each objective is its own LilScript build (effort level 12, lazy_functions).

| | lil2 | upstream, best minifier | difference | |---|---:|---:|---:| | raw | 74,981 | 95,678 (Terser) | −21.6% | | gzip (9) | 24,071 | 26,065 (Terser) | −7.7% | | Brotli (11) | 20,971 | 23,016 (Terser) | −8.9% |

Speed, upstream → lil2: markdown with GFM to HTML, median per call in a fresh browser context per lane, after checking that both give the same output (Playwright; Chromium 151, Firefox 153; AMD EPYC 7763 64-Core Processor). Cold rows are the first import and the first call of a fresh page.

| | Chromium | Firefox | |---|---:|---:| | gfm (15 KB) | 13.6 → 5.35 ms (0.39×) | 27.0 → 12.0 ms (0.44×) | | readme (26 KB) | 22.4 → 8.45 ms (0.38×) | 39.0 → 17.0 ms (0.44×) | | import, cold | 5.80 → 6.00 ms | 13.0 → 13.0 ms | | first call, cold | 57.0 → 46.2 ms | 73.0 → 50.0 ms |

Behaviour

test/differential.test.mjs parses 1,453 documents (all 672 examples of the GFM spec, cmark-gfm's extension tests, GFM edge cases and the CommonMark corpus) with micromark-extension-gfm + mdast-util-gfm and with lil2, and compares the mdast (with and without singleTilde) and the hast (with and without dangerous HTML) as rows of indexed arrays: every node, field and position. test/browser.test.mjs does the same with the browser build in Chromium and Firefox. All are equal.

License

MIT; see NOTICE.md.