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nodeca

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Description

JavaScript YAML parser and dumper. Very fast.

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JS-YAML - YAML 1.2 parser / writer for JavaScript

Name: js-yaml
Brand: js-yaml
SKU: //nodeca/js-yaml
Rating: 4.471 (5239 reviews)

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

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: `DEFAULTSCHEMA`)_ - 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

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: `DEFAULTSCHEMA`)_ 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"
  "empty"       -> ""

!!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

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