uuidv7-js

UUIDv7 generator library for JavaScript, RFC 9562 compliant. Supports encoding/decoding UUIDs to custom alphabets.

Installation

``sh
npm i uuidv7-js
`

Usage

`typescript
import { UUIDv7, uuidv7, encodeUUIDv7, decodeUUIDv7 } from "uuidv7-js";

// Initialize a new UUIDv7 generator.
// You can pass a custom encoding alphabet here.
const uuid = new UUIDv7();

const id = uuid.gen(); // 018ef3e8-90e2-7be4-b4ea-4be3bf8803b7
const encoded = uuid.encode(id); // CANANjseoigQthQMd1VwC
const decoded = uuid.decode(encoded); // 018ef3e8-90e2-7be4-b4ea-4be3bf8803b7
const isValid = UUIDv7.isValid(id); // true
const timestamp = UUIDv7.timestamp(id); // 1713489088738
const date = UUIDv7.date(id); // 2024-04-19T01:11:28.738Z

// You can also use convenient function aliases if you don't need to use a custom alphabet.
const id = uuidv7(); // 018ef3e8-90e2-7be4-b4ea-4be3bf8803b7
const encoded = encodeUUIDv7(id); // CANANjseoigQthQMd1VwC
const decoded = decodeUUIDv7(encoded); // // 018ef3e8-90e2-7be4-b4ea-4be3bf8803b7
`

Create a new instance

`typescript
const uuid = new UUIDv7(opts?: { encodeAlphabet?: string })
`

Creates a new UUIDv7 instance. By default it uses the Base58 alphabet to encode and decode UUIDs, but you can pass a custom alphabet (16-64 characters).

$3

#### gen

`typescript
gen(customTimestamp?: number) => string
`

Generates a new UUIDv7. You can provide a custom timestamp to be used instead of the current one.

#### genMany

`typescript
genMany(amount: number, customTimestamp?: number) => string[]
`

Generates a custom amount of UUIDv7s. You can provide a custom timestamp to be used instead of the current one.

#### encode

`typescript
encode(id: string) => string
`

Encodes a UUIDv7 using the alphabet passed to the constructor or the default one.

#### decode

`typescript
decode(encodedId: string) => string | null
`

Decodes an encoded UUIDv7 using the alphabet passed to the constuctor or the default one. If the UUIDv7 is not valid, null is returned.

#### decodeOrThrow

`typescript
decodeOrThrow(encodedId: string) => string
`

Decodes an encoded UUIDv7 using the alphabet passed to the constuctor or the default one. If the UUIDv7 is not valid, an error is thrown.

$3

#### UUIDv7.isValid

`typescript
UUIDv7.isValid(id: string) => boolean
`

Checks if the UUIDv7 is valid.

#### UUIDv7.timestamp

`typescript
UUIDv7.timestamp(id: string) => number | null
`

Returns the timestamp part of the UUIDv7. If the UUIDv7 is not valid, null is returned.

#### UUIDv7.date

`typescript
UUIDv7.date(id: string) => Date | null
`

Returns the timestamp part of the UUIDv7 converted to Date. If the UUIDv7 is not valid, null is returned.

$3

The library provides a few function aliases for convenience. You can use them without creating a new UUIDv7 instance:

| Function name | Instance method | Description |
| --------------------- | --------------- | --------------------------------------------------------------------------------------------- |
| uuidv7 | gen | Generates a new UUIDv7. |
| encodeUUIDv7 | encode | Encodes a UUIDv7 with the default Base58 alphabet. |
| decodeUUIDv7 | decode | Decodes an encoded UUIDv7 from Base58 alphabet. Returns null if the encoded ID is invalid. |
| decodeOrThrowUUIDv7 | decodeOrThrow | Decodes an encoded UUIDv7 from Base58 alphabet. Throws an error if the encoded ID is invalid. |

Implementation details

This library implements the RFC 9562 spec to generate UUIDv7s:

- if the current timestamp is ahead of the last stored one, it generates new rand_a and rand_b parts;
- if the current timestamp is behind the last stored one, it waits for the next valid timestamp to return a UUIDv7 with newly generated rand_a and rand_b parts;
- if the current timestamp is the same as the last stored one:
- it uses rand_b and then rand_a as randomly seeded counters, in that order. rand_b is the primary counter, and rand_a is used as the secondary one, when rand_b overflows its 62 bits (rare case). When used as a counter, rand_b increments its previous random value by a random integer between 1 and 4,294,967,296 (2^32), and rand_a increments its previous random value by 1, while generating a new rand_b part.
- if both counters overflow their bit sizes, the generation function waits for the next millisecond to return a UUIDv7 with newly generated random parts.

This approach follows the method 2 of the "Monotonicity and Counters" section of the spec. It guarantees monotonicity and uniqueness per instance, and always keeps timestamp the same as Date.now() value.

If you provide a custom timestamp, it will be used instead of the current one. Generation works differently in this case:

- if the custom timestamp is different from the last custom stored one, it generates new rand_a and rand_b parts;
- if the custom timestamp is the same as the last custom stored one, it uses rand_b and then rand_a as randomly seeded counters, in that order, just like the normal generation method. If both rand_a and rand_b overflow, though, the generator creates new rand_a and rand_b parts. This breaks monotonicity per instance with custom timestamp, but ensures that a valid UUIDv7 is always returned. Keep in mind that this is an extremely rare case and should really never happen.

Field and Bit Layout

This is the UUIDv7 Field and Bit Layout, took from the spec linked above:

`
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unix_ts_ms |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unix_ts_ms | ver | rand_a |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|var| rand_b |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| rand_b |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
``

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#### unix_ts_ms

48 bit big-endian unsigned number of Unix epoch timestamp in milliseconds as per Section 6.1. Occupies bits 0 through 47 (octets 0-5).

#### ver

The 4 bit version field as defined by Section 4.2, set to 0b0111 (7). Occupies bits 48 through 51 of octet 6.

#### rand_a

12 bits pseudo-random data to provide uniqueness as per Section 6.9 and/or optional constructs to guarantee additional monotonicity as per Section 6.2. Occupies bits 52 through 63 (octets 6-7).

#### var

The 2 bit variant field as defined by Section 4.1, set to 0b10. Occupies bits 64 and 65 of octet 8.

#### rand_b

The final 62 bits of pseudo-random data to provide uniqueness as per Section 6.9 and/or an optional counter to guarantee additional monotonicity as per Section 6.2. Occupies bits 66 through 127 (octets 8-15).

Feedback

If you found a bug in the implementation, please open a new issue.

Alternatives

- uuidv7 by LiosK

License

This project is licensed under the MIT License.