npm package: @gerhobbelt/js-yaml
Description: YAML 1.2 parser and serializer
Author: Vladimir Zapparov
Latest version: 3.13.1-6

JS-YAML - YAML 1.2 parser / writer for JavaScript
=================================================

[![Build Status](https://travis-ci.org/nodeca/js-yaml.svg?branch=master)](https://travis-ci.org/nodeca/js-yaml)
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[![Required Node](https://img.shields.io/node/v/js-yaml.svg)](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
```


### Bundled YAML library for browsers

``` html
<!-- esprima required only for !!js/function -->
<script src="esprima.js"></script>
<script src="js-yaml.min.js"></script>
<script type="text/javascript">
var doc = jsyaml.load('greeting: hello\nname: world');
</script>
```

Browser support was done mostly for the online demo. If you find any errors - feel
free to send pull requests with fixes. Also note, that IE and other old browsers
needs [es5-shims](https://github.com/kriskowal/es5-shim) to operate.

Notes:

1. We have no resources to support browserified version. Don't expect it to be
   well tested. Don't expect fast fixes if something goes wrong there.
2. `!!js/function` in browser bundle will not work by default. If you really need
   it - load `esprima` parser first (via amd or directly).
3. `!!bin` in browser will return `Array`, because browsers do not support
   node.js `Buffer` and adding Buffer shims is completely useless on practice.


API
---

Here we cover the most 'useful' methods. If you need advanced details (creating
your own tags), see [wiki](https://github.com/nodeca/js-yaml/wiki) and
[examples](https://github.com/nodeca/js-yaml/tree/master/examples) for more
info.

``` javascript
yaml = require('js-yaml');
fs   = require('fs');

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


### safeLoad (string [ , options ])

**Recommended loading way.** Parses `string` as single YAML document. Returns a JavaScript
object or throws `YAMLException` on error. By default, does not support regexps,
functions, modules and undefined. This method is safe for untrusted data.

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_SAFE_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_SAFE_SCHEMA` - all supported YAML types, without unsafe ones
    (`!!js/undefined`, `!!js/regexp` and `!!js/function`):
    http://yaml.org/type/
  - `DEFAULT_FULL_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.
- `metaKey` _(default: null)_ - if set, then saves start line and start position of each field under this key into the resulting object.
- `legacy` _(default: false)_ - check for non-ASCII line breaks in the file and throw an exception when any exist in the YAML input
- `listener` _(default: null)_ - function which is invoked for YAML parse events. (Currently the element `open` and `close` events are emitted for every YAML node)

NOTE: the `safeLoad` function **does not** understand multi-document sources, it throws
an exception on those.

NOTE: JS-YAML **does not** support schema-specific tag resolution restrictions.
So, the JSON schema is not as strictly defined as 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.


### load (string [ , options ])

**Use with care with untrusted sources**. The same as `safeLoad()` but uses
`DEFAULT_FULL_SCHEMA` by default - adds some JavaScript-specific types:
`!!js/function`, `!!js/module`, `!!js/regexp` and `!!js/undefined`. For untrusted sources, you
must additionally validate object structure to avoid injections:

``` javascript
var untrusted_code = '"toString": !<tag:yaml.org,2002:js/function> "function (){very_evil_thing();}"';

// I'm just converting that string, what could possibly go wrong?
require('js-yaml').load(untrusted_code) + ''
```


### safeLoadAll (string [, iterator [, options ]])

Same as `safeLoad()`, but understands multi-document sources. Applies
`iterator` to each document if specified. 

Returns an array of documents, listing the documents in order of appearance in the input.

The `iterator` callback interface includes these parameters:

- `doc`: the parsed document object
- `index`: the index number of the document, starting at *0*
- `options_state`: a reference to the active js-yaml options in the js-yaml `state` object

``` javascript
var yaml = require('js-yaml');

yaml.safeLoadAll(data, function (doc, index, options_state) {
  console.log(doc);
});
```


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

Same as `safeLoadAll()` but uses `DEFAULT_FULL_SCHEMA` by default.


### safeDump (object [ , options ])

Serializes `object` as a YAML document. Uses `DEFAULT_SAFE_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_SAFE_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.
- `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. See also `quoteKeys`.
- `quoteKeys` _(default: `false`)_ - if `true`, all keys will be quoted in doublequotes (`"`). Eg. `'{"a": b}'`. Other valid options are `'` and `"` to specify the type of quotes. In combination with `condenseFlow`, this generates `'{"a":b}'`. Useful if no spaces are wanted in the dump (eg. URL).
- `scalarQuoteStyle` _(default: `null`)_ set the quote style for scalar values. Valid values are `"single"` and `"double"`. Double quoted values will not be changed to single quotes.

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
  "blank"       -> '' +++++
  "canonical"   -> "~"
  "lowercase"   => "null"
  "uppercase"   -> "NULL"
  "camelcase"   -> "Null"

!!int
  "binary"      -> "0b1", "0b101010", "0b1110001111010"
  "octal"       -> "01", "052", "016172"
  "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
safeDump (object, {
  'styles': {
    '!!null': 'canonical' // dump null as ~
  },
  'sortKeys': true        // sort object keys
});
```

### dump (object [ , options ])

Same as `safeDump()` but without limits (uses `DEFAULT_FULL_SCHEMA` by default).


Supported YAML types
--------------------

The list of standard YAML tags and corresponding JavaScipt 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**

```
!!js/regexp /pattern/gim            # RegExp
!!js/undefined ''                   # Undefined
!!js/function 'function () {...}'   # Function
```

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
```


Breaking changes in 2.x.x -> 3.x.x
----------------------------------

If you have not used __custom__ tags or loader classes and not loaded yaml
files via `require()`, no changes are needed. Just upgrade the library.

Otherwise, you should:

1. Replace all occurrences of `require('xxxx.yml')` by `fs.readFileSync()` +
  `yaml.safeLoad()`.
2. rewrite your custom tags constructors and custom loader
  classes, to conform the new API. See
  [examples](https://github.com/nodeca/js-yaml/tree/master/examples) and
  [wiki](https://github.com/nodeca/js-yaml/wiki) for details.


License
-------

View the [LICENSE](https://github.com/nodeca/js-yaml/blob/master/LICENSE) file
(MIT).