# uid-generator

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Generates cryptographically strong, pseudo-random UIDs with custom size and base-encoding. Generated UIDs are strings that are guaranteed to always be the same length depending on the specified [bit-size](#api).

Great for generating things like compact API keys and UIDs that are safe to use in URLs and cookies.

**Tip:** The main benefit of this module is the ability to easily generate human-safe UIDs (using [base58](#uidgeneratorbase58--string)) and large UIDs that are more compact (using something like [base94](#uidgeneratorbase94--string)). If you’re just looking to generate URL-safe base64 IDs, the best package for that is [`uid-safe`](https://github.com/crypto-utils/uid-safe).


## Installation

```sh
npm install uid-generator --save
# or
yarn add uid-generator
```


## Usage

```js
const UIDGenerator = require('uid-generator');
const uidgen = new UIDGenerator(); // Default is a 128-bit UID encoded in base58

// Async with `await`
await uidgen.generate(); // -> 'B1q2hUEKmeVp9zWepx9cnp'

// Async with promise
uidgen.generate()
  .then(uid => console.log(uid)); // -> 'PXmRJVrtzFAHsxjs7voD5R'

// Async with callback
uidgen.generate((err, uid) => {
  if (err) throw err;
  console.log(uid); // -> '4QhmRwHwwrgFqXULXNtx4d'
});

// Sync
uidgen.generateSync(); // -> '8Vw3bgbMMzeYfrQHQ8p3Jr'
```


## API

### new UIDGenerator([bitSize][, baseEncoding])

Creates a new `UIDGenerator` instance that generates `bitSize`-bit or `uidLength`-sized UIDs encoded using the characters in `baseEncoding`.

| Param          | Type     | Default               | Description
|----------------|--------- |-----------------------|-------------
| [bitSize]      | `number` | `128`                 | The size of the UID to generate in bits. Must be a multiple of `8`.
| [baseEncoding] | `string` | `UIDGenerator.BASE58` | One of the `UIDGenerator.BASE##` constants or a custom string of characters to use to encode the UID.

**Note:** If a custom `baseEncoding` that has URL-unsafe characters is used, it is up to you to URL-encode the resulting UID.

**Example**

```js
new UIDGenerator();
new UIDGenerator(256);
new UIDGenerator(UIDGenerator.BASE16);
new UIDGenerator(512, UIDGenerator.BASE62);
new UIDGenerator('01'); // Custom encoding (base2)
```

---

### uidgen.generate([cb]) ⇒ `?Promise<string>`

Asynchronously generates a UID.

| Param | Type | Description |
|-------|------|-------------|
| [cb] | `?function(error, uid)` | An optional callback that will be called with the results of generating the UID.<br>If not specified, the function will return a promise. |

**Returns**: `?Promise<string>` - A promise that will resolve with the UID or reject with an error. Returns nothing if the `cb` parameter is specified.

**`async`/`await` Example**

```js
const uidgen = new UIDGenerator();
// This must be inside an async function
const uid = await uidgen.generate();
```

**Promise Example**

```js
const uidgen = new UIDGenerator();

uidgen.generate()
  .then(uid => {
    // Use uid here
  });
```

**Callback Example**

```js
const uidgen = new UIDGenerator();

uidgen.generate((err, uid) => {
  if (err) throw err;
  // Use uid here
});
```

---

### uidgen.generateSync() ⇒ `string`

Synchronously generates a UID.

**Returns**: `string` - The generated UID.

**Example**

```js
const uidgen = new UIDGenerator();
const uid = uidgen.generateSync();
```

---

### (readonly) uidgen.bitSize : `number`

The size of the UID that will be generated in bits (the `bitSize` value passed to the `UIDGenerator` constructor).
If the `uidLength` parameter is passed to the constructor instead of `bitSize`, `bitSize` is calculated as follows:

```js
bitSize = Math.ceil(length * Math.log2(base));
```

**Example**

```js
new UIDGenerator().bitSize // -> 128
new UIDGenerator(256).bitSize // -> 256
```

---

### (readonly) uidgen.uidLength : `number`

The length of the UID string that will be generated. The generated UID will always be this length.
This will be the same as the `uidLength` parameter passed to the `UIDGenerator` constructor.
If the `uidLength` parameter is not passed to the constructor, it will be calculated using the `bitSize` parameter as follows:

```js
uidLength = Math.ceil(bitSize / Math.log2(base))
```

**Example**

```js
new UIDGenerator().uidLength // -> 22
new UIDGenerator(256, UIDGenerator.BASE62).uidLength // -> 43
```

---

### (readonly) uidgen.baseEncoding : `string`

The set of characters used to encode the UID string (the `baseEncoding` value passed to the `UIDGenerator` constructor).

**Example**

```js
new UIDGenerator().baseEncoding // -> '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
new UIDGenerator(UIDGenerator.BASE16).baseEncoding // -> '0123456789abcdef'
new UIDGenerator('01').baseEncoding // -> '01'
```

---

### (readonly) uidgen.base : `number`

The base of the UID that will be generated (which is the number of characters in the `baseEncoding`).

**Example**

```js
new UIDGenerator().base // -> 58
new UIDGenerator(UIDGenerator.BASE16).base // -> 16
new UIDGenerator('01').base // -> 2
```

---

### UIDGenerator.BASE16 : `string`
`0123456789abcdef`

### UIDGenerator.BASE36 : `string`
`0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ`

### UIDGenerator.BASE58 : `string`
`123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz`

(all alphanumeric characters except for `0`, `O`, `I`, and `l` — characters easily mistaken for each other)

The default base.

**Tip:** Use this base to create UIDs that are easy to type in manually.

### UIDGenerator.BASE62 : `string`
`0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz`

### UIDGenerator.BASE66 : `string`
`0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-._~`

(all ASCII characters that do not need to be encoded in a URI as specified by [RFC 3986](https://tools.ietf.org/html/rfc3986#section-2.3))

### UIDGenerator.BASE71 : `string`
`0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!'()*-._~`

(all ASCII characters that are not encoded by `encodeURIComponent()`)

### UIDGenerator.BASE94 : `string`
``!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~``

(all readable ASCII characters)