gray-matter

What is gray-matter?

The gray-matter npm package is used to parse front-matter from strings or files. Front-matter is metadata stored at the top of a file, typically in YAML or JSON format, which is often used in static site generators and other content management systems.

What are gray-matter's main functionalities?

Parsing Front-Matter

This feature allows you to parse front-matter from a string. The front-matter is typically written in YAML or JSON format and is separated from the content by triple dashes (---). The parsed object contains the metadata and the content separately.

const matter = require('gray-matter');
const file = '---\ntitle: Hello World\ndate: 2023-10-01\n---\nThis is the content of the file.';
const parsed = matter(file);
console.log(parsed);

Stringify Front-Matter

This feature allows you to convert a content string and a metadata object back into a string with front-matter. This is useful for generating files with front-matter programmatically.

const matter = require('gray-matter');
const data = { title: 'Hello World', date: '2023-10-01' };
const content = 'This is the content of the file.';
const stringified = matter.stringify(content, data);
console.log(stringified);

Custom Delimiters

This feature allows you to specify custom delimiters for the front-matter. By default, gray-matter uses triple dashes (---), but you can change this to any string you prefer.

const matter = require('gray-matter');
const file = '+++\ntitle = "Hello World"\ndate = "2023-10-01"\n+++\nThis is the content of the file.';
const parsed = matter(file, { delimiters: '+++' });
console.log(parsed);

Other packages similar to gray-matter

front-matter

The front-matter package is another tool for parsing front-matter from strings. It is simpler and has fewer features compared to gray-matter, but it is also lightweight and easy to use.

js-yaml

The js-yaml package is primarily used for parsing and stringifying YAML, but it can also be used to handle front-matter. It is more general-purpose and powerful for YAML processing, but it requires more setup to use for front-matter specifically.

marked

The marked package is a markdown parser that can also handle front-matter if used in conjunction with other tools. It is more focused on converting markdown to HTML, but it can be extended to support front-matter parsing.

README

gray-matter

A simple-to-use Front-Matter parsing and extraction Library.

• Use custom delimiters
• Will extract and parse YAML, JSON, or CoffeeScript.
• Easy to add additional parsers!

Quickstart

Install with npm

npm i gray-matter --save

Install with bower

bower install gray-matter --save

• Quickstart
• Usage
• Methods
  • matter
  • matter.read
  • matter.exists
  • matter.extend
  • matter.recontruct
  • matter.stringify
  • matter.stringifyYAML
• Options
  • lang
  • delims
  • autodetect
• Examples
  • matter
  • matter.extend
• Authors
• License

Usage

var matter = require('gray-matter');
matter(String, Object);

Methods

matter

By default the matter() method expects a string. So this:

matter(str);

results in something like:

{
  "context": {"foo": "bar"},
  "content": "baz",
  "original": "---\nfoo: bar\n---\nbaz"
}

matter.read

Read a file from the file system before parsing.

matter.read('file.md');

Returns:

{
  "context": {"foo": "bar"},
  "content": "baz",
  "original": "---\nfoo: bar\n---\nbaz"
}

matter.exists

Returns true or false if front matter exists:

matter.exists(str);

matter.extend

Extend and stringify YAML front matter. Takes an object as the second parameter, and returns either the extended, stringified object (YAML), or if no front matter is found an empty string is returned.

matter.extend(str, obj);

matter.recontruct

A convenience wrapper around the matter and matter.extend. Extends YAML front matter, then re-assembles front matter with the content of the file.

matter.recontruct(str, obj);

matter.stringify

A convenience wrapper around the matter(str).context method.

matter.stringify(str);

matter.stringifyYAML

Stringify parsed front matter back to YAML.

matter.stringifyYAML(str);

Options

All methods will accept an options object to be passed as a second paramer

lang

Type: String

Default: yaml

The parser to use on the extracted front matter. Valid options are, yaml, coffee and json.

delims

Type: Object

Default: {delims: ['---', '---']}

Open and close delimiters can be passed in as an array of strings. Example:

matter.read('file.md', {delims: ['~~~', '~~~']});

You may also pass an array of arrays, allowing multiple alternate delimiters to be used. Example:

{
  delims: [
    ['---', '~~~'], ['---', '~~~']
  ]
}

Note that passing multiple delimiters will yield unpredictable results, so it is recommended that you use this option only for testing purposes.

autodetect

Type: Boolean

Default: undefined

Attempts to automatically register a language that is specified after the first code boundary (delimiter).

Usage Example:

--- coffee
user = 'jonschlinkert'
reverse = (src) ->
  src.split('').reverse().join('')
---
{%= user %}
{%= reverse(user) %}

Examples

matter

Let's say our page, foo.html contains

---
title: YAML Front matter
description: This is a page
---
<h1>{{title}}</h1>

then running the following in the command line:

console.log(matter('foo.html'));

returns

{
  "context": {
    "title": "YAML Front matter",
    "description": "This is a page"
  },
  "content": "<h1>{{title}}</h1>",
  "original": "---\ntitle: YAML Front matter\n---\n<h1>{{title}}</h1>"
}

and

console.log(matter('foo.html').context);

returns

{"title": "YAML Front matter", "description": "This is a page"}

matter.extend

Given this page:

---
title: Gray Matter
---
Hooray!

and this config:

var file = require('fs').readFileSync('file.md', 'utf8');
var obj = {
  description: 'A simple to use front matter lib';
};
matter.extend(file, obj);

the result would be:

---
title: Gray Matter
description: A simple to use front matter lib
---
Hooray!

Authors

Jon Schlinkert

• github/jonschlinkert
• twitter/jonschlinkert

Brian Woodward

• github/doowb
• twitter/doowb

License

Copyright (c) 2014 Jon Schlinkert, Brian Woodward, contributors. Released under the MIT license

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This file was generated by grunt-readme on Monday, January 27, 2014.