setup-node/node_modules/uuid/README_js.md

```javascript --hide
runmd.onRequire = path => path.replace(/^uuid/, './');
```

# uuid [![Build Status](https://secure.travis-ci.org/kelektiv/node-uuid.svg?branch=master)](http://travis-ci.org/kelektiv/node-uuid) #

Simple, fast generation of [RFC4122](http://www.ietf.org/rfc/rfc4122.txt) UUIDS.

Features:

* Support for version 1, 3, 4 and 5 UUIDs
* Cross-platform
* Uses cryptographically-strong random number APIs (when available)
* Zero-dependency, small footprint (... but not [this small](https://gist.github.com/982883))

[**Deprecation warning**: The use of `require('uuid')` is deprecated and will not be
supported after version 3.x of this module.  Instead, use `require('uuid/[v1|v3|v4|v5]')` as shown in the examples below.]

## Quickstart - CommonJS (Recommended)

```shell
npm install uuid
```

Then generate your uuid version of choice ...

Version 1 (timestamp):

```javascript --run v1
const uuidv1 = require('uuid/v1');
uuidv1(); // RESULT
```

Version 3 (namespace):

```javascript --run v3
const uuidv3 = require('uuid/v3');

// ... using predefined DNS namespace (for domain names)
uuidv3('hello.example.com', uuidv3.DNS); // RESULT

// ... using predefined URL namespace (for, well, URLs)
uuidv3('http://example.com/hello', uuidv3.URL); // RESULT

// ... using a custom namespace
//
// Note: Custom namespaces should be a UUID string specific to your application!
// E.g. the one here was generated using this modules `uuid` CLI.
const MY_NAMESPACE = '1b671a64-40d5-491e-99b0-da01ff1f3341';
uuidv3('Hello, World!', MY_NAMESPACE); // RESULT
```

Version 4 (random):

```javascript --run v4
const uuidv4 = require('uuid/v4');
uuidv4(); // RESULT
```

Version 5 (namespace):

```javascript --run v5
const uuidv5 = require('uuid/v5');

// ... using predefined DNS namespace (for domain names)
uuidv5('hello.example.com', uuidv5.DNS); // RESULT

// ... using predefined URL namespace (for, well, URLs)
uuidv5('http://example.com/hello', uuidv5.URL); // RESULT

// ... using a custom namespace
//
// Note: Custom namespaces should be a UUID string specific to your application!
// E.g. the one here was generated using this modules `uuid` CLI.
const MY_NAMESPACE = '1b671a64-40d5-491e-99b0-da01ff1f3341';
uuidv5('Hello, World!', MY_NAMESPACE); // RESULT
```

## Quickstart - Browser-ready Versions

Browser-ready versions of this module are available via [wzrd.in](https://github.com/jfhbrook/wzrd.in).

For version 1 uuids:

```html
<script src="http://wzrd.in/standalone/uuid%2Fv1@latest"></script>
<script>
uuidv1(); // -> v1 UUID
</script>
```

For version 3 uuids:

```html
<script src="http://wzrd.in/standalone/uuid%2Fv3@latest"></script>
<script>
uuidv3('http://example.com/hello', uuidv3.URL); // -> v3 UUID
</script>
```

For version 4 uuids:

```html
<script src="http://wzrd.in/standalone/uuid%2Fv4@latest"></script>
<script>
uuidv4(); // -> v4 UUID
</script>
```

For version 5 uuids:

```html
<script src="http://wzrd.in/standalone/uuid%2Fv5@latest"></script>
<script>
uuidv5('http://example.com/hello', uuidv5.URL); // -> v5 UUID
</script>
```

## API

### Version 1

```javascript
const uuidv1 = require('uuid/v1');

// Incantations
uuidv1();
uuidv1(options);
uuidv1(options, buffer, offset);
```

Generate and return a RFC4122 v1 (timestamp-based) UUID.

* `options` - (Object) Optional uuid state to apply. Properties may include:

  * `node` - (Array) Node id as Array of 6 bytes (per 4.1.6). Default: Randomly generated ID.  See note 1.
  * `clockseq` - (Number between 0 - 0x3fff) RFC clock sequence.  Default: An internally maintained clockseq is used.
  * `msecs` - (Number) Time in milliseconds since unix Epoch.  Default: The current time is used.
  * `nsecs` - (Number between 0-9999) additional time, in 100-nanosecond units. Ignored if `msecs` is unspecified. Default: internal uuid counter is used, as per 4.2.1.2.

* `buffer` - (Array | Buffer) Array or buffer where UUID bytes are to be written.
* `offset` - (Number) Starting index in `buffer` at which to begin writing.

Returns `buffer`, if specified, otherwise the string form of the UUID

Note: The <node> id is generated guaranteed to stay constant for the lifetime of the current JS runtime. (Future versions of this module may use persistent storage mechanisms to extend this guarantee.)

Example: Generate string UUID with fully-specified options

```javascript --run v1
const v1options = {
  node: [0x01, 0x23, 0x45, 0x67, 0x89, 0xab],
  clockseq: 0x1234,
  msecs: new Date('2011-11-01').getTime(),
  nsecs: 5678
};
uuidv1(v1options); // RESULT
```

Example: In-place generation of two binary IDs

```javascript --run v1
// Generate two ids in an array
const arr = new Array();
uuidv1(null, arr, 0);  // RESULT
uuidv1(null, arr, 16); // RESULT
```

### Version 3

```javascript
const uuidv3 = require('uuid/v3');

// Incantations
uuidv3(name, namespace);
uuidv3(name, namespace, buffer);
uuidv3(name, namespace, buffer, offset);
```

Generate and return a RFC4122 v3 UUID.

* `name` - (String | Array[]) "name" to create UUID with
* `namespace` - (String | Array[]) "namespace" UUID either as a String or Array[16] of byte values
* `buffer` - (Array | Buffer) Array or buffer where UUID bytes are to be written.
* `offset` - (Number) Starting index in `buffer` at which to begin writing. Default = 0

Returns `buffer`, if specified, otherwise the string form of the UUID

Example:

```javascript --run v3
uuidv3('hello world', MY_NAMESPACE);  // RESULT
```

### Version 4

```javascript
const uuidv4 = require('uuid/v4')

// Incantations
uuidv4();
uuidv4(options);
uuidv4(options, buffer, offset);
```

Generate and return a RFC4122 v4 UUID.

* `options` - (Object) Optional uuid state to apply. Properties may include:
  * `random` - (Number[16]) Array of 16 numbers (0-255) to use in place of randomly generated values
  * `rng` - (Function) Random # generator function that returns an Array[16] of byte values (0-255)
* `buffer` - (Array | Buffer) Array or buffer where UUID bytes are to be written.
* `offset` - (Number) Starting index in `buffer` at which to begin writing.

Returns `buffer`, if specified, otherwise the string form of the UUID

Example: Generate string UUID with predefined `random` values

```javascript --run v4
const v4options = {
  random: [
    0x10, 0x91, 0x56, 0xbe, 0xc4, 0xfb, 0xc1, 0xea,
    0x71, 0xb4, 0xef, 0xe1, 0x67, 0x1c, 0x58, 0x36
  ]
};
uuidv4(v4options); // RESULT
```

Example: Generate two IDs in a single buffer

```javascript --run v4
const buffer = new Array();
uuidv4(null, buffer, 0);  // RESULT
uuidv4(null, buffer, 16); // RESULT
```

### Version 5

```javascript
const uuidv5 = require('uuid/v5');

// Incantations
uuidv5(name, namespace);
uuidv5(name, namespace, buffer);
uuidv5(name, namespace, buffer, offset);
```

Generate and return a RFC4122 v5 UUID.

* `name` - (String | Array[]) "name" to create UUID with
* `namespace` - (String | Array[]) "namespace" UUID either as a String or Array[16] of byte values
* `buffer` - (Array | Buffer) Array or buffer where UUID bytes are to be written.
* `offset` - (Number) Starting index in `buffer` at which to begin writing. Default = 0

Returns `buffer`, if specified, otherwise the string form of the UUID

Example:

```javascript --run v5
uuidv5('hello world', MY_NAMESPACE);  // RESULT
```

## Command Line

UUIDs can be generated from the command line with the `uuid` command.

```shell
$ uuid
ddeb27fb-d9a0-4624-be4d-4615062daed4

$ uuid v1
02d37060-d446-11e7-a9fa-7bdae751ebe1
```

Type `uuid --help` for usage details

## Testing

```shell
npm test
```