mdast extensions to parse and serialize GFM tables.

• What is this?
• When to use this
• Install
• Use
• API
  • gfmTableFromMarkdown
  • gfmTableToMarkdown(options?)
  • Options
• Examples
  • Example: stringLength
• HTML
• Syntax
• Syntax tree
  • Nodes
  • Enumeration
  • Content model
• Types
• Compatibility
• Related
• Contribute
• License

This package contains two extensions that add support for GFM table syntax in markdown to mdast. These extensions plug into mdast-util-from-markdown (to support parsing tables in markdown into a syntax tree) and mdast-util-to-markdown (to support serializing tables in syntax trees to markdown).

You can use these extensions when you are working with mdast-util-from-markdown and mdast-util-to-markdown already.

When working with mdast-util-from-markdown, you must combine this package with micromark-extension-gfm-table.

When you don’t need a syntax tree, you can use micromark directly with micromark-extension-gfm-table.

When you are working with syntax trees and want all of GFM, use mdast-util-gfm instead.

All these packages are used remark-gfm, which focusses on making it easier to transform content by abstracting these internals away.

This utility does not handle how markdown is turned to HTML. That’s done by mdast-util-to-hast.

This package is ESM only. In Node.js (version 16+), install with npm:

npm install mdast-util-gfm-table

In Deno with esm.sh:

import {gfmTableFromMarkdown, gfmTableToMarkdown} from 'https://esm.sh/mdast-util-gfm-table@2'

In browsers with esm.sh:

<script type="module">
  import {gfmTableFromMarkdown, gfmTableToMarkdown} from 'https://esm.sh/mdast-util-gfm-table@2?bundle'
</script>

Say our document example.md contains:

| a | b | c | d |
| - | :- | -: | :-: |
| e | f |
| g | h | i | j | k |

…and our module example.js looks as follows:

import fs from 'node:fs/promises'
import {gfmTable} from 'micromark-extension-gfm-table'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {gfmTableFromMarkdown, gfmTableToMarkdown} from 'mdast-util-gfm-table'
import {toMarkdown} from 'mdast-util-to-markdown'

const doc = await fs.readFile('example.md')

const tree = fromMarkdown(doc, {
  extensions: [gfmTable()],
  mdastExtensions: [gfmTableFromMarkdown()]
})

console.log(tree)

const out = toMarkdown(tree, {extensions: [gfmTableToMarkdown()]})

console.log(out)

…now running node example.js yields (positional info removed for brevity):

{
  type: 'root',
  children: [
    {
      type: 'table',
      align: [null, 'left', 'right', 'center'],
      children: [
        {
          type: 'tableRow',
          children: [
            {type: 'tableCell', children: [{type: 'text', value: 'a'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'b'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'c'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'd'}]}
          ]
        },
        {
          type: 'tableRow',
          children: [
            {type: 'tableCell', children: [{type: 'text', value: 'e'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'f'}]}
          ]
        },
        {
          type: 'tableRow',
          children: [
            {type: 'tableCell', children: [{type: 'text', value: 'g'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'h'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'i'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'j'}]},
            {type: 'tableCell', children: [{type: 'text', value: 'k'}]}
          ]
        }
      ]
    }
  ]
}

| a | b  |  c |  d  |   |
| - | :- | -: | :-: | - |
| e | f  |    |     |   |
| g | h  |  i |  j  | k |

This package exports the identifiers gfmTableFromMarkdown and gfmTableToMarkdown. There is no default export.

Create an extension for mdast-util-from-markdown to enable GFM tables in markdown.

Extension for mdast-util-from-markdown to enable GFM tables (FromMarkdownExtension).

Create an extension for mdast-util-to-markdown to enable GFM tables in markdown.

• options (Options, optional) — configuration

Extension for mdast-util-to-markdown to enable GFM tables (ToMarkdownExtension).

Configuration (TypeScript type).

• tableCellPadding (boolean, default: true) — whether to add a space of padding between delimiters and cells
• tablePipeAlign (boolean, default: true) — whether to align the delimiters
• stringLength (((value: string) => number), default: s => s.length) — function to detect the length of table cell content, used when aligning the delimiters between cells

It’s possible to align tables based on the visual width of cells. First, let’s show the problem:

import {gfmTable} from 'micromark-extension-gfm-table'
import {fromMarkdown} from 'mdast-util-from-markdown'
import {gfmTableFromMarkdown, gfmTableToMarkdown} from 'mdast-util-gfm-table'
import {toMarkdown} from 'mdast-util-to-markdown'

const doc = `| Alpha | Bravo |
| - | - |
| 中文 | Charlie |
| 👩‍❤️‍👩 | Delta |`

const tree = fromMarkdown(doc, {
  extensions: [gfmTable],
  mdastExtensions: [gfmTableFromMarkdown]
})

console.log(toMarkdown(tree, {extensions: [gfmTableToMarkdown()]}))

The above code shows how these utilities can be used to format markdown. The output is as follows:

| Alpha    | Bravo   |
| -------- | ------- |
| 中文       | Charlie |
| 👩‍❤️‍👩 | Delta   |

To improve the alignment of these full-width characters and emoji, pass a stringLength function that calculates the visual width of cells. One such algorithm is string-width. It can be used like so:

@@ -2,6 +2,7 @@ import {gfmTable} from 'micromark-extension-gfm-table'
 import {fromMarkdown} from 'mdast-util-from-markdown'
 import {gfmTableFromMarkdown, gfmTableToMarkdown} from 'mdast-util-gfm-table'
 import {toMarkdown} from 'mdast-util-to-markdown'
+import stringWidth from 'string-width'

 const doc = `| Alpha | Bravo |
 | - | - |
@@ -13,4 +14,8 @@ const tree = fromMarkdown(doc, {
   mdastExtensions: [gfmTableFromMarkdown()]
 })

-console.log(toMarkdown(tree, {extensions: [gfmTableToMarkdown()]}))
+console.log(
+  toMarkdown(tree, {
+    extensions: [gfmTableToMarkdown({stringLength: stringWidth})]
+  })
+)

The output of our code with these changes is as follows:

| Alpha | Bravo   |
| ----- | ------- |
| 中文  | Charlie |
| 👩‍❤️‍👩    | Delta   |

This utility does not handle how markdown is turned to HTML. That’s done by mdast-util-to-hast.

See Syntax in micromark-extension-gfm-table.

The following interfaces are added to mdast by this utility.

interface Table <: Parent {
  type: 'table'
  align: [alignType]?
  children: [TableContent]
}

Table (Parent) represents two-dimensional data.

Table can be used where flow content is expected. Its content model is table content.

The head of the node represents the labels of the columns.

An align field can be present. If present, it must be a list of alignTypes. It represents how cells in columns are aligned.

For example, the following markdown:

| foo | bar |
| :-- | :-: |
| baz | qux |

Yields:

{
  type: 'table',
  align: ['left', 'center'],
  children: [
    {
      type: 'tableRow',
      children: [
        {
          type: 'tableCell',
          children: [{type: 'text', value: 'foo'}]
        },
        {
          type: 'tableCell',
          children: [{type: 'text', value: 'bar'}]
        }
      ]
    },
    {
      type: 'tableRow',
      children: [
        {
          type: 'tableCell',
          children: [{type: 'text', value: 'baz'}]
        },
        {
          type: 'tableCell',
          children: [{type: 'text', value: 'qux'}]
        }
      ]
    }
  ]
}

interface TableRow <: Parent {
  type: "tableRow"
  children: [RowContent]
}

TableRow (Parent) represents a row of cells in a table.

TableRow can be used where table content is expected. Its content model is row content.

If the node is a head, it represents the labels of the columns for its parent Table.

For an example, see Table.

interface TableCell <: Parent {
  type: "tableCell"
  children: [PhrasingContent]
}

TableCell (Parent) represents a header cell in a Table, if its parent is a head, or a data cell otherwise.

TableCell can be used where row content is expected. Its content model is phrasing content excluding Break nodes.

For an example, see Table.

enum alignType {
  'center' | 'left' | 'right' | null
}

alignType represents how phrasing content is aligned ([CSSTEXT]).

• 'left': See the left value of the text-align CSS property
• 'right': See the right value of the text-align CSS property
• 'center': See the center value of the text-align CSS property
• null: phrasing content is aligned as defined by the host environment

type FlowContentGfm = Table | FlowContent

type TableContent = TableRow

Table content represent the rows in a table.

type RowContent = TableCell

Row content represent the cells in a row.

This package is fully typed with TypeScript. It exports the additional type Options.

The Table, TableRow, and TableCell types of the mdast nodes are exposed from @types/mdast.

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, mdast-util-gfm-table@^2, compatible with Node.js 16.

This utility works with mdast-util-from-markdown version 2+ and mdast-util-to-markdown version 2+.

• remarkjs/remark-gfm — remark plugin to support GFM
• syntax-tree/mdast-util-gfm — same but all of GFM (autolink literals, footnotes, strikethrough, tables, tasklists)
• micromark/micromark-extension-gfm-table — micromark extension to parse GFM tables

See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

MIT © Titus Wormer