js-yaml/README.md

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)
[![NPM version](https://img.shields.io/npm/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 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 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 throw on warnings if this function is not provided.
- `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.

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, JSON schema is not as strict as defined in the YAML specification.
It allows numbers in any notation, use `Null` and `NULL` as `null`, etc.
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/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 and apply
`iterator` to each document.

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

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


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

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


### safeDump (object [ , options ])

Serializes `object` as YAML document. Uses `DEFAULT_SAFE_SCHEMA`, so it will
throw exception if you try to dump regexps or functions. However, you can
disable exceptions by `skipInvalid` option.

options:

- `indent` _(default: 2)_ - indentation width to use (in spaces).
- `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

The following table show availlable styles (e.g. "canonical",
"binary"...) available for each tag (.e.g. !!null, !!int ...). Yaml
ouput 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"       -> "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 array 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 needed. Just upgrade library.

Otherwise, you should:

1. Replace all occurences of `require('xxxx.yml')` by `fs.readFileSync()` +
  `yaml.safeLoad()`.
2. rewrite your custom tags constructors and custom loader
  classes, to conform 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).