JS-YAML - YAML 1.2 parser / writer for JavaScript
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#id2802346JSON_SCHEMA - all JSON-supported types:
http://www.yaml.org/spec/1.2/spec.html#id2803231CORE_SCHEMA - same as JSON_SCHEMA:
http://www.yaml.org/spec/1.2/spec.html#id2804923DEFAULT_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 elementsskipInvalid (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 everwherestyles - "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 referencesnoCompatMode (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 1.1condenseFlow (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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