JS-YAML - YAML 1.2 parser / writer for JavaScript
=================================================
[](https://travis-ci.org/nodeca/js-yaml)
[](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
styles:
``` none
!!null
"canonical" => "~"
!!int
"binary" => "0b1", "0b101010", "0b1110001111010"
"octal" => "01", "052", "016172"
"decimal" => "1", "42", "7290"
"hexadecimal" => "0x1", "0x2A", "0x1C7A"
!!null, !!bool, !!float
"lowercase" => "null", "true", "false", ".nan", '.inf'
"uppercase" => "NULL", "TRUE", "FALSE", ".NAN", '.INF'
"camelcase" => "Null", "True", "False", ".NaN", '.Inf'
```
By default, !!int uses `decimal`, and !!null, !!bool, !!float use `lowercase`.
### 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).