js-yaml vs yaml vs yamljs
YAML Parsing and Stringifying Comparison
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What's YAML Parsing and Stringifying?

YAML (YAML Ain't Markup Language) is a human-readable data serialization format often used for configuration files, data exchange, and more. In JavaScript, libraries like js-yaml, yaml, and yamljs provide tools for parsing YAML files into JavaScript objects and stringifying objects back into YAML format. These libraries are essential for applications that need to read from or write to YAML files, offering features like support for complex data types, custom serialization, and more. js-yaml is a widely-used library known for its simplicity and performance, while yaml offers a modern API with advanced features like streaming and custom tags. yamljs, on the other hand, focuses on ease of use and provides a straightforward interface for working with YAML in JavaScript.

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js-yaml156,223,1896,423-674 years agoMIT
yaml84,680,8041,477683 kB21a month agoISC
yamljs2,554,206889-538 years agoMIT
Feature Comparison: js-yaml vs yaml vs yamljs

Parsing and Stringifying

  • js-yaml:

    js-yaml provides efficient parsing and stringifying of YAML, supporting complex data structures, custom tags, and error handling. It is known for its reliability and performance, making it suitable for a wide range of applications.

  • yaml:

    yaml offers advanced parsing and stringifying capabilities with support for streaming, custom tags, and more. It is designed for performance and flexibility, allowing for better handling of large YAML files and complex data types.

  • yamljs:

    yamljs offers basic parsing and stringifying of YAML with a focus on simplicity. It supports standard YAML features but lacks some of the advanced capabilities found in js-yaml and yaml, making it more suitable for straightforward use cases.

Streaming Support

  • js-yaml:

    js-yaml does not natively support streaming for parsing or stringifying YAML. It processes the entire input at once, which can be a limitation for very large YAML files.

  • yaml:

    yaml provides built-in streaming support for both parsing and stringifying, allowing for more efficient handling of large YAML files. This feature reduces memory consumption and improves performance when working with extensive data.

  • yamljs:

    yamljs does not support streaming. It reads and writes YAML data in a single operation, which may lead to high memory usage with large files.

Custom Tags

  • js-yaml:

    js-yaml supports custom tags, allowing developers to define their own data types and serialization methods. This feature provides flexibility for handling non-standard YAML structures.

  • yaml:

    yaml also supports custom tags and offers more advanced features, including better handling of tag resolution and serialization. It allows for more complex and flexible implementations of custom data types.

  • yamljs:

    yamljs supports custom tags but with limited functionality compared to js-yaml and yaml. It allows for basic customization of how certain data types are handled during parsing and stringifying.

Error Handling

  • js-yaml:

    js-yaml provides basic error handling for parsing and stringifying operations, including informative error messages for syntax errors and invalid data.

  • yaml:

    yaml offers more robust error handling, including support for asynchronous parsing and detailed error reporting. It is designed to handle errors more gracefully, especially in complex YAML structures.

  • yamljs:

    yamljs provides simple error handling for parsing errors but is less comprehensive than js-yaml and yaml. It may not provide detailed error messages for all types of parsing issues.

Ease of Use: Code Examples

  • js-yaml:

    js-yaml Example

    const yaml = require('js-yaml');
const fs = require('fs');

// Parse YAML
const doc = yaml.load(fs.readFileSync('file.yaml', 'utf8'));
console.log(doc);

// Stringify YAML
const yamlStr = yaml.dump(doc);
console.log(yamlStr);
  • yaml:

    yaml Example

    const { parse, stringify } = require('yaml');
const fs = require('fs');

// Parse YAML
const doc = parse(fs.readFileSync('file.yaml', 'utf8'));
console.log(doc);

// Stringify YAML
const yamlStr = stringify(doc);
console.log(yamlStr);
  • yamljs:

    yamljs Example

    const YAML = require('yamljs');

// Parse YAML
const doc = YAML.load('file.yaml');
console.log(doc);

// Stringify YAML
const yamlStr = YAML.stringify(doc);
console.log(yamlStr);
How to Choose: js-yaml vs yaml vs yamljs
  • js-yaml:

    Choose js-yaml if you need a reliable, well-established library for parsing and dumping YAML with good performance and compatibility. It is suitable for most use cases and has a simple API.

  • yaml:

    Choose yaml if you want a modern, feature-rich library that supports advanced YAML features, streaming, and custom serialization. It is ideal for projects that require more flexibility and performance optimizations.

  • yamljs:

    Choose yamljs if you prefer a lightweight library with a simple API for quick YAML parsing and stringifying tasks. It is great for smaller projects or when you need a straightforward solution without many dependencies.

Similar Npm Packages to js-yaml

js-yaml is a popular JavaScript library for parsing and dumping YAML (YAML Ain't Markup Language) data. It allows developers to easily convert YAML data into JavaScript objects and vice versa, making it a valuable tool for applications that require configuration files or data serialization in YAML format. While js-yaml is widely used, there are several alternatives in the ecosystem that also provide YAML parsing and manipulation capabilities. Here are a few notable alternatives:

  • yaml is a modern YAML parser and serializer for JavaScript. It aims to provide a more robust and feature-rich alternative to js-yaml, with support for advanced YAML features and better performance. The library is designed to be easy to use and integrates well with both Node.js and browser environments. If you are looking for a library that offers more features and better performance for handling YAML data, yaml is a great option.
  • yaml-front-matter is a specialized library that focuses on parsing YAML front matter, which is commonly used in static site generators like Jekyll and Gatsby. This library allows developers to easily extract front matter from documents, making it particularly useful for managing metadata in markdown files. If your project involves working with markdown files that include YAML front matter, yaml-front-matter is a convenient choice.
  • yamljs is another library for parsing and dumping YAML in JavaScript. It offers a simple API for converting YAML to JavaScript objects and vice versa. While it may not have as many features as some of the other libraries, it is lightweight and easy to use, making it suitable for smaller projects or applications that require basic YAML functionality.

For a detailed comparison of these libraries, check out the link: Comparing js-yaml vs yaml vs yaml-front-matter vs yamljs.

Similar Npm Packages to yaml

yaml is a JavaScript library for parsing and stringifying YAML (YAML Ain't Markup Language) data. It provides a straightforward way to work with YAML files in Node.js and browser environments, making it easier for developers to read and write configuration files, data exchange formats, and more. While yaml is a robust option for handling YAML data, there are other libraries available that serve similar purposes. Here are a couple of alternatives:

  • js-yaml is a widely used library for parsing and dumping YAML in JavaScript. It is known for its simplicity and ease of use, making it a popular choice among developers. js-yaml supports both Node.js and browser environments and offers features such as custom type handling and support for complex data structures. If you need a reliable and well-documented library for working with YAML in your JavaScript projects, js-yaml is an excellent option.
  • yamljs is another library for parsing and stringifying YAML in JavaScript. It is lightweight and designed to be easy to use, making it suitable for projects that require basic YAML functionality without the overhead of more complex libraries. yamljs allows you to convert YAML to JavaScript objects and vice versa, making it a good choice for simple applications or scripts that need to handle YAML data.

To compare these libraries, check out the following link: Comparing js-yaml vs yaml vs yamljs.

Similar Npm Packages to yamljs

yamljs is a JavaScript library that allows developers to parse and stringify YAML (YAML Ain't Markup Language) files easily. It provides a straightforward API for working with YAML data, making it a popular choice for applications that require configuration files or data interchange in a human-readable format. While yamljs is a solid option for handling YAML, there are other libraries available that also serve this purpose. Here are a few alternatives:

  • js-yaml is a widely used library for parsing and dumping YAML in JavaScript. It is known for its performance and flexibility, supporting both Node.js and browser environments. js-yaml is particularly useful for developers who need to work with YAML in various contexts, such as server-side applications or client-side scripts. Its robust feature set and active community make it a reliable choice for handling YAML data.
  • yaml is another modern YAML parser and serializer for JavaScript. It aims to provide a more complete and user-friendly interface compared to other libraries. yaml supports advanced features such as custom types and schema validation, making it suitable for complex applications that require more than just basic YAML parsing and stringification. If you need a library that offers both simplicity and advanced capabilities, yaml is an excellent option.

To see how yamljs compares with js-yaml and yaml, check out the comparison: Comparing js-yaml vs yaml vs yamljs.

README for js-yaml

JS-YAML - YAML 1.2 parser / writer for JavaScript

CI NPM version

Online Demo

This is an implementation of YAML, a human-friendly data serialization language. Started as PyYAML port, it was completely rewritten from scratch. Now it's very fast, and supports 1.2 spec.

Installation

YAML module for node.js

npm install js-yaml

CLI executable

If you want to inspect your YAML files from CLI, install js-yaml globally:

npm install -g js-yaml

Usage

usage: js-yaml [-h] [-v] [-c] [-t] file

Positional arguments:
  file           File with YAML document(s)

Optional arguments:
  -h, --help     Show this help message and exit.
  -v, --version  Show program's version number and exit.
  -c, --compact  Display errors in compact mode
  -t, --trace    Show stack trace on error

API

Here we cover the most 'useful' methods. If you need advanced details (creating your own tags), see examples for more info.

const yaml = require('js-yaml');
const fs   = require('fs');

// Get document, or throw exception on error
try {
  const doc = yaml.load(fs.readFileSync('/home/ixti/example.yml', 'utf8'));
  console.log(doc);
} catch (e) {
  console.log(e);
}

load (string [ , options ])

Parses string as single YAML document. Returns either a plain object, a string, a number, null or undefined, or throws YAMLException on error. By default, does not support regexps, functions and undefined.

options:

  • filename (default: null) - string to be used as a file path in error/warning messages.
  • onWarning (default: null) - function to call on warning messages. Loader will call this function with an instance of YAMLException for each warning.
  • schema (default: DEFAULT_SCHEMA) - specifies a schema to use.
    • FAILSAFE_SCHEMA - only strings, arrays and plain objects: http://www.yaml.org/spec/1.2/spec.html#id2802346
    • JSON_SCHEMA - all JSON-supported types: http://www.yaml.org/spec/1.2/spec.html#id2803231
    • CORE_SCHEMA - same as JSON_SCHEMA: http://www.yaml.org/spec/1.2/spec.html#id2804923
    • DEFAULT_SCHEMA - all supported YAML types.
  • json (default: false) - compatibility with JSON.parse behaviour. If true, then duplicate keys in a mapping will override values rather than throwing an error.

NOTE: This function does not understand multi-document sources, it throws exception on those.

NOTE: JS-YAML does not support schema-specific tag resolution restrictions. So, the JSON schema is not as strictly defined in the YAML specification. It allows numbers in any notation, use Null and NULL as null, etc. The core schema also has no such restrictions. It allows binary notation for integers.

loadAll (string [, iterator] [, options ])

Same as load(), but understands multi-document sources. Applies iterator to each document if specified, or returns array of documents.

const yaml = require('js-yaml');

yaml.loadAll(data, function (doc) {
  console.log(doc);
});

dump (object [ , options ])

Serializes object as a YAML document. Uses DEFAULT_SCHEMA, so it will throw an exception if you try to dump regexps or functions. However, you can disable exceptions by setting the skipInvalid option to true.

options:

  • indent (default: 2) - indentation width to use (in spaces).
  • noArrayIndent (default: false) - when true, will not add an indentation level to array elements
  • skipInvalid (default: false) - do not throw on invalid types (like function in the safe schema) and skip pairs and single values with such types.
  • flowLevel (default: -1) - specifies level of nesting, when to switch from block to flow style for collections. -1 means block style everwhere
  • styles - "tag" => "style" map. Each tag may have own set of styles.
  • schema (default: DEFAULT_SCHEMA) specifies a schema to use.
  • sortKeys (default: false) - if true, sort keys when dumping YAML. If a function, use the function to sort the keys.
  • lineWidth (default: 80) - set max line width. Set -1 for unlimited width.
  • noRefs (default: false) - if true, don't convert duplicate objects into references
  • noCompatMode (default: false) - if true don't try to be compatible with older yaml versions. Currently: don't quote "yes", "no" and so on, as required for YAML 1.1
  • condenseFlow (default: false) - if true flow sequences will be condensed, omitting the space between a, b. Eg. '[a,b]', and omitting the space between key: value and quoting the key. Eg. '{"a":b}' Can be useful when using yaml for pretty URL query params as spaces are %-encoded.
  • quotingType (' or ", default: ') - strings will be quoted using this quoting style. If you specify single quotes, double quotes will still be used for non-printable characters.
  • forceQuotes (default: false) - if true, all non-key strings will be quoted even if they normally don't need to.
  • replacer - callback function (key, value) called recursively on each key/value in source object (see replacer docs for JSON.stringify).

The following table show availlable styles (e.g. "canonical", "binary"...) available for each tag (.e.g. !!null, !!int ...). Yaml output is shown on the right side after => (default setting) or ->:

!!null
  "canonical"   -> "~"
  "lowercase"   => "null"
  "uppercase"   -> "NULL"
  "camelcase"   -> "Null"

!!int
  "binary"      -> "0b1", "0b101010", "0b1110001111010"
  "octal"       -> "0o1", "0o52", "0o16172"
  "decimal"     => "1", "42", "7290"
  "hexadecimal" -> "0x1", "0x2A", "0x1C7A"

!!bool
  "lowercase"   => "true", "false"
  "uppercase"   -> "TRUE", "FALSE"
  "camelcase"   -> "True", "False"

!!float
  "lowercase"   => ".nan", '.inf'
  "uppercase"   -> ".NAN", '.INF'
  "camelcase"   -> ".NaN", '.Inf'

Example:

dump(object, {
  'styles': {
    '!!null': 'canonical' // dump null as ~
  },
  'sortKeys': true        // sort object keys
});

Supported YAML types

The list of standard YAML tags and corresponding JavaScript types. See also YAML tag discussion and YAML types repository.

!!null ''                   # null
!!bool 'yes'                # bool
!!int '3...'                # number
!!float '3.14...'           # number
!!binary '...base64...'     # buffer
!!timestamp 'YYYY-...'      # date
!!omap [ ... ]              # array of key-value pairs
!!pairs [ ... ]             # array or array pairs
!!set { ... }               # array of objects with given keys and null values
!!str '...'                 # string
!!seq [ ... ]               # array
!!map { ... }               # object

JavaScript-specific tags

See js-yaml-js-types for extra types.

Caveats

Note, that you use arrays or objects as key in JS-YAML. JS does not allow objects or arrays as keys, and stringifies (by calling toString() method) them at the moment of adding them.

---
? [ foo, bar ]
: - baz
? { foo: bar }
: - baz
  - baz

{ "foo,bar": ["baz"], "[object Object]": ["baz", "baz"] }

Also, reading of properties on implicit block mapping keys is not supported yet. So, the following YAML document cannot be loaded.

&anchor foo:
  foo: bar
  *anchor: duplicate key
  baz: bat
  *anchor: duplicate key

js-yaml for enterprise

Available as part of the Tidelift Subscription

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