fenceparser

A metadata parser for code fences in markdown

• What’s this?
• Install
• Use
• API
  • Options
  • Syntax
• Examples
  • Example: single range
  • Example: multiple ranges
  • Example: ranges with custom annotations
  • Example: key-value pairs
  • Example: customizing the default range's key
• Development
• License

What’s this?

Many markdown processors can parse the language token associated with a code fence. fenceparser is meant for parsing other metadata besides language token. It supports

• ranges, (e.g., {1} {3, 7} ins{9..11, 88} del{90, 101..167}) and
• key-value pairs (e.g., caption='Hello, World')

Install

This package is ESM only.

In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install @microflash/fenceparser

In Deno, with esm.sh:

import fenceparser from "https://esm.sh/@microflash/fenceparser";

In browsers, with esm.sh:

<script type="module">
  import fenceparser from "https://esm.sh/@microflash/fenceparser?bundle";
</script>

Use

Say, you have the following code fence

```js {1} {3, 7} {9..11, 88} {90, 101..112} text-color='--text-default' syntax_theme="nord" css=`{ *: { display: none }}`

remark will provide the meta and lang for the above code fence.

{
  "lang": "js",
  "meta": "{1} {3, 7} {9..11, 88} {90, 101..112} text-color='--text-default' syntax_theme=\"nord\" css=`{ *: { display: none }}`"
}

Use the fenceparser to parse the meta as follows.

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser();
console.log(parser.parse("{1} {3, 7} {9..11, 88} {90, 101..112} text-color='--text-default' syntax_theme=\"nord\" css=`{ *: { display: none }}`"));

Running the above example yields.

{
  'text-color': '--text-default',
  syntax_theme: 'nord',
  css: '{ *: { display: none }}',
  highlight: [
    1, 3, 7, 9, 10, 11, 88,  
  ],
  ins: [
    90, 101, 102, 103, 104, 105,
    106, 107, 108, 109, 110, 111, 
    112,
  ]
}

API

The default export is FenceParser class.

Options

The following options are available. All of them are optional.

• rangeKey (default: highlight): specifies the key for the default range of numbers

Syntax

Key-value pairs

• The key and value must be separated by equality sign =.
• The value must be wrapped within single-quotes ', double-quotes " or backticks `.
• The key can contain letters, digits, underscore, and hyphen.

Ranges

• A range can be a single number, or a pair of numbers denoting the start and end values separated by double-dots ...
• A range must be specified in curly braces.
• Multiple ranges can be specified in a single pair of curly braces. They should be separated by comma ,.
• Ranges can also be annotated; the annotation should be prefixed before the starting curly brace. The default annotation is highlight. You can customize this annotation by passing rangeKey value in the parser options.
• Ranges will be grouped in a single array by their annotations.

Examples

Example: single range

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser();
console.log(parser.parse("{100}"));

Running the above example yields.

{
  highlight: [
    100,
  ]
}

Example: multiple ranges

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser();
console.log(parse("{3, 7} {9..11, 101..105}"));

Running the above example yields.

{
  highlight: [
    1, 3, 7, 9, 10, 11,
    101, 102, 103, 104, 105,
  ],
}

Example: ranges with custom annotations

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser();
console.log(parse("{3, 7} ins{9..11, 13} del{101..105}"));

Running the above example yields.

{
  highlight: [
    3, 7,
  ],
  ins: [
    9, 10, 11, 13,
  ],
  del: [
    101, 102, 103, 104, 105,
  ],
}

Example: key-value pairs

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser();
console.log(parse("data-theme='synthwave' callback=`(code) => copyToClipboard(code)`"));

Running the above example yields.

{
  'data-theme': 'synthwave',
  callback: '(code) => copyToClipboard(code)',
}

Example: customizing the default range's key

import FenceParser from "@microflash/fenceparser";

const parser = new FenceParser({ rangeKey: "mark" });
console.log(parser.parse("{100}"));

Running the above example yields.

{
  mark: [
    100,
  ]
}

Check the fixtures for more examples on the syntax.

Development

Any changes in the parser should have corresponding tests.

Run the tests with the following command.

pnpm test

License

MIT