YAML

yaml is a JavaScript parser and stringifier for YAML, a human friendly data serialization standard. It supports both parsing and stringifying data using all versions of YAML, along with all common data schemas. As a particularly distinguishing feature, yaml fully supports reading and writing comments in YAML documents.

The library is released under the ISC open source license, and the code is available on GitHub. It has no external dependencies, and is usable in both browser and node environments.

For more information, see the project's documentation site: eemeli.org/yaml

To install:

npm install yaml
# or
yarn add yaml

Note: yaml 0.x and 1.x are rather different implementations. For the earlier yaml, see tj/js-yaml.

API Overview

The API provided by yaml has three layers, depending on how deep you need to go: Pure JavaScript, YAML Documents, and the CST Parser. The first has the simplest API and "just works", the second gets you all the bells and whistles supported by the library along with a decent AST, and the third is the closest to YAML source, making it fast, raw, and crude.

import YAML from 'yaml'
// or
const YAML = require('yaml').default

Pure JavaScript

• YAML.parse(str, options): value
• YAML.stringify(value, options): string

YAML Documents

• YAML.createNode(value, wrapScalars): Node
• YAML.defaultOptions
• YAML.Document
  • constructor(options)
  • defaults
  • #anchors
  • #contents
  • #errors
• YAML.parseAllDocuments(str, options): YAML.Document[]
• YAML.parseDocument(str, options): YAML.Document

import Map from 'yaml/map'
import Pair from 'yaml/pair'
import Seq from 'yaml/seq'

• new Map()
• new Pair(key, value)
• new Seq()

CST Parser

import parseCST from 'yaml/parse-cst'

• parseCST(str): CSTDocument[]
• YAML.parseCST(str): CSTDocument[]

YAML.parse

# file.yml
YAML:
  - A human-readable data serialization language
  - https://en.wikipedia.org/wiki/YAML
yaml:
  - A complete JavaScript implementation
  - https://www.npmjs.com/package/yaml

import fs from 'fs'
import YAML from 'yaml'

YAML.parse('3.14159')
// 3.14159

YAML.parse('[ true, false, maybe, null ]\n')
// [ true, false, 'maybe', null ]

const file = fs.readFileSync('./file.yml', 'utf8')
YAML.parse(file)
// { YAML:
//   [ 'A human-readable data serialization language',
//     'https://en.wikipedia.org/wiki/YAML' ],
//   yaml:
//   [ 'A complete JavaScript implementation',
//     'https://www.npmjs.com/package/yaml' ] }

YAML.stringify

import YAML from 'yaml'

YAML.stringify(3.14159)
// '3.14159\n'

YAML.stringify([true, false, 'maybe', null])
// `- true
// - false
// - maybe
// - null
// `

YAML.stringify({ number: 3, plain: 'string', block: 'two\nlines\n' })
// `number: 3
// plain: string
// block: >
//   two
//
//   lines
// `