JS-YAML - YAML 1.2 parser / writer for JavaScript
=================================================
[](https://github.com/nodeca/js-yaml/actions)
[](https://www.npmjs.org/package/js-yaml)
__[Online Demo](http://nodeca.github.com/js-yaml/)__
This is an implementation of [YAML](http://yaml.org/), a human-friendly data
serialization language. Started as [PyYAML](http://pyyaml.org/) 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](https://github.com/nodeca/js-yaml/tree/master/examples)
for more info.
``` javascript
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.
``` javascript
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 `->`:
``` none
!!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:
``` javascript
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](http://pyyaml.org/wiki/YAMLTagDiscussion) and
[YAML types repository](http://yaml.org/type/).
```
!!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](https://github.com/nodeca/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.
``` yaml
---
? [ foo, bar ]
: - baz
? { foo: bar }
: - baz
- baz
```
``` javascript
{ "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.
``` yaml
&anchor foo:
foo: bar
*anchor: duplicate key
baz: bat
*anchor: duplicate key
```
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----------------------
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