@yankeeinlondon/gray-matter
Advanced tools
Parse front-matter from a string or file. Fast, reliable and easy to use. Parses YAML front matter by default, but also has support for YAML, JSON, TOML or Coffee Front-Matter, with options to set custom delimiters. Used by metalsmith, assemble, verb and
Parse front-matter from a string or file. Fast, reliable and easy to use. Parses YAML front matter by default, but also has support for YAML, JSON, TOML or Coffee Front-Matter, with options to set custom delimiters. Used by metalsmith, assemble, verb and many other projects.
Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your :heart: and support.
NOTE: in this release we have switched over to ES Modules in the core code but both ESM and CJS are exported for users of this library.
Install with npm:
npm install --save gray-matter
Please see the changelog to learn about breaking changes that were made in v3.0.
Add the HTML in the following example to example.html, then add the following code to example.js and run $ node example (without the $):
import fs from 'node:fs';
import matter from 'gray-matter';
const str = fs.readFileSync('example.html', 'utf8');
console.log(matter(str));
Converts a string with front-matter, like this:
---
title: Hello
slug: home
---
<h1>Hello world!</h1>
Into an object like this:
{
content: '<h1>Hello world!</h1>',
data: {
title: 'Hello',
slug: 'home'
}
}
Why did we create gray-matter in the first place?
We created gray-matter after trying out other libraries that failed to meet our standards and requirements.
Some libraries met most of the requirements, but none met all of them.
Here are the most important:
data: the parsed YAML front matter, as a JSON objectcontent: the contents as a string, without the front matterorig: the "original" content (for debugging)Both JS and TS use the modern "import" signature that hopefully you are familiar with:
import matter from 'gray-matter';
Pass a string and options to gray-matter:
console.log(matter('---\ntitle: Front Matter\n---\nThis is content.'));
Returns:
{
content: '\nThis is content.',
data: {
title: 'Front Matter'
}
}
More about the returned object in the following section.
gray-matter returns a file object with the following properties.
file.data {Object}: the object created by parsing front-matterfile.content {String}: the input string, with matter strippedfile.excerpt {String}: an excerpt, if defined on the optionsfile.empty {String}: when the front-matter is "empty" (either all whitespace, nothing at all, or just comments and no data), the original string is set on this property. See #65 for details regarding use case.file.isEmpty {Boolean}: true if front-matter is empty.In addition, the following non-enumberable properties are added to the object to help with debugging.
file.orig {Buffer}: the original input string (or buffer)file.language {String}: the front-matter language that was parsed. yaml is the defaultfile.matter {String}: the raw, un-parsed front-matter stringfile.stringify {Function}: stringify the file by converting file.data to a string in the given language, wrapping it in delimiters and prepending it to file.content.If you'd like to test-drive the examples, first clone gray-matter into my-project (or wherever you want):
git clone https://github.com/jonschlinkert/gray-matter my-project
CD into my-project and install dependencies:
cd my-project && npm install
Then run any of the examples to see how gray-matter works:
node examples/<example_name>
Takes a string or object with content property, extracts and parses front-matter from the string, then returns an object with data, content and other useful properties.
Params
input {Object|String}: String, or object with content stringoptions {Object}returns {Object}Example
import matter from 'gray-matter';
console.log(matter('---\ntitle: Home\n---\nOther stuff'));
//=> { data: { title: 'Home'}, content: 'Other stuff' }
Stringify an object to YAML or the specified language, and append it to the given string. By default, only YAML and JSON can be stringified. See the engines section to learn how to stringify other languages.
Params
file {String|Object}: The content string to append to stringified front-matter, or a file object with file.content string.data {Object}: Front matter to stringify.options {Object}: Options to pass to gray-matter and js-yaml.returns {String}: Returns a string created by wrapping stringified yaml with delimiters, and appending that to the given string.Example
console.log(matter.stringify('foo bar baz', {title: 'Home'}));
// results in:
// ---
// title: Home
// ---
// foo bar baz
Synchronously read a file from the file system and parse front matter. Returns the same object as the main function.
Params
filepath {String}: file path of the file to read.options {Object}: Options to pass to gray-matter.returns {Object}: Returns an object with data and contentExample
const file = matter.read('./content/blog-post.md');
Returns true if the given string has front matter.
Params
string {String}options {Object}returns {Boolean}: True if front matter exists.Type: Boolean|Function
Default: undefined
Extract an excerpt that directly follows front-matter, or is the first thing in the string if no front-matter exists.
If set to excerpt: true, it will look for the frontmatter delimiter, --- by default and grab everything leading up to it.
Example
const str = '---\nfoo: bar\n---\nThis is an excerpt.\n---\nThis is content';
const file = matter(str, { excerpt: true });
Results in:
{
content: 'This is an excerpt.\n---\nThis is content',
data: { foo: 'bar' },
excerpt: 'This is an excerpt.\n'
}
You can also set excerpt to a function. This function uses the 'file' and 'options' that were initially passed to gray-matter as parameters, so you can control how the excerpt is extracted from the content.
Example
// returns the first 4 lines of the contents
function firstFourLines(file, options) {
file.excerpt = file.content.split('\n').slice(0, 4).join(' ');
}
const file = matter([
'---',
'foo: bar',
'---',
'Only this',
'will be',
'in the',
'excerpt',
'but not this...'
].join('\n'), {excerpt: firstFourLines});
Results in:
{
content: 'Only this\nwill be\nin the\nexcerpt\nbut not this...',
data: { foo: 'bar' },
excerpt: 'Only this will be in the excerpt'
}
Type: String
Default: undefined
Define a custom separator to use for excerpts.
console.log(matter(string, {excerpt_separator: '<!-- end -->'}));
Example
The following HTML string:
---
title: Blog
---
My awesome blog.
<!-- end -->
<h1>Hello world</h1>
Results in:
{
data: { title: 'Blog'},
excerpt: 'My awesome blog.',
content: 'My awesome blog.\n<!-- end -->\n<h1>Hello world</h1>'
}
Define custom engines for parsing and/or stringifying front-matter.
Type: Object Object of engines
Default: JSON, YAML and JavaScript are already handled by default.
Engine format
Engines may either be an object with parse and (optionally) stringify methods, or a function that will be used for parsing only.
Examples
const toml = require('toml');
/**
* defined as a function
*/
const file = matter(str, {
engines: {
toml: toml.parse.bind(toml),
}
});
/**
* Or as an object
*/
const file = matter(str, {
engines: {
toml: {
parse: toml.parse.bind(toml),
// example of throwing an error to let users know stringifying is
// not supported (a TOML stringifier might exist, this is just an example)
stringify: function() {
throw new Error('cannot stringify to TOML');
}
}
}
});
console.log(file);
Type: String
Default: yaml
Define the engine to use for parsing front-matter.
console.log(matter(string, {language: 'toml'}));
Example
The following HTML string:
---
title = "TOML"
description = "Front matter"
categories = "front matter toml"
---
This is content
Results in:
{ content: 'This is content',
excerpt: '',
data:
{ title: 'TOML',
description: 'Front matter',
categories: 'front matter toml' } }
Dynamic language detection
Instead of defining the language on the options, gray-matter will automatically detect the language defined after the first delimiter and select the correct engine to use for parsing.
---toml
title = "TOML"
description = "Front matter"
categories = "front matter toml"
---
This is content
Type: String
Default: ---
Open and close delimiters can be passed in as an array of strings.
Example:
// format delims as a string
matter.read('file.md', {delims: '~~~'});
// or an array (open/close)
matter.read('file.md', {delims: ['~~~', '~~~']});
would parse:
~~~
title: Home
~~~
This is the {{title}} page.
Decrecated, please use options.language instead.
Decrecated, please use options.delimiters instead.
Decrecated, please use options.engines instead.
Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
npm install && npm test
(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)
To generate the readme, run the following command:
npm install -g verbose/verb#dev verb-generate-readme && verb
You might also be interested in these projects:
| Commits | Contributor |
|---|---|
| 174 | jonschlinkert |
| 7 | RobLoach |
| 5 | heymind |
| 4 | doowb |
| 3 | aljopro |
| 2 | reccanti |
| 2 | onokumus |
| 2 | moozzyk |
| 1 | Ajedi32 |
| 1 | caesar |
| 1 | ianstormtaylor |
| 1 | qm3ster |
| 1 | zachwhaley |
Jon Schlinkert
Copyright © 2018, Jon Schlinkert. Released under the MIT License.
This file was generated by verb-generate-readme, v0.6.0, on April 01, 2018.
FAQs
Parse front-matter from a string or file. Fast, reliable and easy to use. Parses YAML front matter by default, but also has support for YAML, JSON, TOML or Coffee Front-Matter, with options to set custom delimiters. Used by metalsmith, assemble, verb and
We found that @yankeeinlondon/gray-matter demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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