Note: Ordering of values in the byte arrays used by `parse()` and `stringify()` follows the left ↠ right order of hex-pairs in UUID strings. As shown in the example below.
| `arr` | `Array`-like collection of 16 values (starting from `offset`) between 0-255. |
| [`offset` = 0] | `Number` Starting index in the Array |
| _returns_ | `String` |
| _throws_ | `TypeError` if a valid UUID string cannot be generated |
Note: Ordering of values in the byte arrays used by `parse()` and `stringify()` follows the left ↠ right order of hex-pairs in UUID strings. As shown in the example below.
Note: The default [node id](https://tools.ietf.org/html/rfc4122#section-4.1.6) (the last 12 digits in the UUID) is generated once, randomly, on process startup, and then remains unchanged for the duration of the process.
Note: `options.random` and `options.rng` are only meaningful on the very first call to `v1()`, where they may be passed to initialize the internal `node` and `clockseq` fields.
This library comes with [ECMAScript Modules](https://www.ecma-international.org/ecma-262/6.0/#sec-modules) (ESM) support for Node.js versions that support it ([example](./examples/node-esmodules/)) as well as bundlers like [rollup.js](https://rollupjs.org/guide/en/#tree-shaking) ([example](./examples/browser-rollup/)) and [webpack](https://webpack.js.org/guides/tree-shaking/) ([example](./examples/browser-webpack/)) (targeting both, Node.js and browser environments).
To run the examples you must first create a dist build of this library in the module root:
```shell
npm run build
```
## CDN Builds
### ECMAScript Modules
To load this module directly into modern browsers that [support loading ECMAScript Modules](https://caniuse.com/#feat=es6-module) you can make use of [jspm](https://jspm.org/):
To load this module directly into older browsers you can use the [UMD (Universal Module Definition)](https://github.com/umdjs/umd) builds from any of the following CDNs:
Methods for the other algorithms ([`uuidv1()`](#uuidv1options-buffer-offset), [`uuidv3()`](#uuidv3name-namespace-buffer-offset) and [`uuidv5()`](#uuidv5name-namespace-buffer-offset)) are available from the files `uuidv1.min.js`, `uuidv3.min.js` and `uuidv5.min.js` respectively.
## "getRandomValues() not supported"
This error occurs in environments where the standard [`crypto.getRandomValues()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues) API is not supported. This issue can be resolved by adding an appropriate polyfill:
1. Import it _before_`uuid`. Since `uuid` might also appear as a transitive dependency of some other imports it's safest to just import `react-native-get-random-values` as the very first thing in your entry point:
```javascript
import'react-native-get-random-values';
import{v4asuuidv4}from'uuid';
```
Note: If you are using Expo, you must be using at least `react-native-get-random-values@1.5.0` and `expo@39.0.0`.
### Web Workers / Service Workers (Edge <= 18)
[In Edge <= 18, Web Crypto is not supported in Web Workers or Service Workers](https://caniuse.com/#feat=cryptography) and we are not aware of a polyfill (let us know if you find one, please).
## Upgrading From `uuid@7.x`
### Only Named Exports Supported When Using with Node.js ESM
`uuid@7.x` did not come with native ECMAScript Module (ESM) support for Node.js. Importing it in Node.js ESM consequently imported the CommonJS source with a default export. This library now comes with true Node.js ESM support and only provides named exports.
Instead of doing:
```javascript
importuuidfrom'uuid';
uuid.v4();
```
you will now have to use the named exports:
```javascript
import{v4asuuidv4}from'uuid';
uuidv4();
```
### Deep Requires No Longer Supported
Deep requires like `require('uuid/v4')` [which have been deprecated in `uuid@7.x`](#deep-requires-now-deprecated) are no longer supported.
## Upgrading From `uuid@3.x`
"_Wait... what happened to `uuid@4.x` - `uuid@6.x`?!?_"
In order to avoid confusion with RFC [version 4](#uuidv4options-buffer-offset) and [version 5](#uuidv5name-namespace-buffer-offset) UUIDs, and a possible [version 6](http://gh.peabody.io/uuidv6/), releases 4 thru 6 of this module have been skipped.
### Deep Requires Now Deprecated
`uuid@3.x` encouraged the use of deep requires to minimize the bundle size of browser builds:
```javascript
constuuidv4=require('uuid/v4');// <== NOW DEPRECATED!
uuidv4();
```
As of `uuid@7.x` this library now provides ECMAScript modules builds, which allow packagers like Webpack and Rollup to do "tree-shaking" to remove dead code. Instead, use the `import` syntax:
```javascript
import{v4asuuidv4}from'uuid';
uuidv4();
```
... or for CommonJS:
```javascript
const{v4:uuidv4}=require('uuid');
uuidv4();
```
### Default Export Removed
`uuid@3.x` was exporting the Version 4 UUID method as a default export:
```javascript
constuuid=require('uuid');// <== REMOVED!
```
This usage pattern was already discouraged in `uuid@3.x` and has been removed in `uuid@7.x`.
