What is yaml?
The 'yaml' npm package is a JavaScript library for parsing and serializing YAML, a human-friendly data serialization standard. It can be used to convert YAML to JSON and vice versa, and to work with YAML content programmatically in JavaScript.
What are yaml's main functionalities?
Parsing YAML to JSON
This feature allows you to parse a string of YAML content and convert it into a JavaScript object.
const yaml = require('yaml');
const yamlText = 'key: value\nnumber: 123';
const jsonObject = yaml.parse(yamlText);
console.log(jsonObject);
Stringifying JSON to YAML
This feature enables you to take a JavaScript object and serialize it into a YAML formatted string.
const yaml = require('yaml');
const jsonObject = { key: 'value', number: 123 };
const yamlText = yaml.stringify(jsonObject);
console.log(yamlText);
Custom Tags
This feature allows you to define custom tags for specialized YAML types, enabling the parsing of YAML content with custom data structures.
const yaml = require('yaml');
const customType = { identify: value => value instanceof Set, tag: 'tag:yaml.org,2002:set', resolve: (doc, cst) => new Set(cst.strValue.split(', ')) };
yaml.defaultOptions.customTags = [customType];
const yamlText = '!!set a, b, c';
const data = yaml.parse(yamlText);
console.log(data);
Other packages similar to yaml
js-yaml
js-yaml is another popular YAML parser and serializer for JavaScript. It offers similar functionality to the 'yaml' package, including parsing and stringifying, and it also provides a safe loading option to prevent executing arbitrary code during parsing.
yamljs
yamljs is a YAML parser and dumper written in JavaScript. It provides functionality similar to 'yaml' and 'js-yaml' but has a different API design and may have different performance characteristics.
YAML
JavaScript parser and stringifier for YAML 1.2
Note: yaml
0.x and 1.x are rather different implementations. For the earlier yaml
, see tj/js-yaml.
Usage
npm install yaml
import { resolve } from 'yaml'
const yaml =
`YAML:
- A human-readable data serialization language
- https://en.wikipedia.org/wiki/YAML
yaml:
- A complete JavaScript implementation
- https://www.npmjs.com/package/yaml
`
const doc = resolve(yaml)[0]
doc.toJSON()
doc.toString() === yaml
Beta Progress
The reason why this project exists is to have a tool that's capable of properly generating and handling YAML files with comments, specifically to provide context for translation strings that have been lifted out of JS source code. We're not there yet, as the prerequisite for that is having a complete and functioning YAML library.
The AST level of the library has been released separately, and is fully functional.
What Works So Far
Parsing
- Support for all YAML node types, including alias nodes and multi-document streams
- Complete support for the Fallback, JSON, and Core Schemas, as well as an "extended" schema that covers all of the YAML 1.1 scalar types except for
!!yaml
. - Support for
<<
merge keys (default-enabled, disable with merge: false
option) - Complete match between the parsed
in.yaml
and in.json
files across all of the yaml-test-suite test cases (note: A few of the tests are not in agreement with the spec, so this requires the use of a custom branch until [PR #24] and issue #25 are resolved) - Comments are parsed and included up to the AST level of the API
- "Native"
Map
and Seq
collections have toJSON()
methods for bare JavaScript Object
and Array
output - Any string input should be accepted, and produce some output. Errors (if any) are not thrown, but included in the document's
errors
array
Stringifying
Document#toString()
mostly works, producing idempotent YAML from all but a few corner casesAST#toString()
works completely, but is clumsy to use
Still Needs Work
- Object creation:
Document
, Map
and Seq
need constructors accepting plain JS objects - Long lines should be wrapped
- Collections need to retain tag and comment data
- Item add/remove should keep tags and comments in place
- Not all parser errors are reported
- API needs finalising