ULID for Deno

ULID is an alternative to UUID with the following features:

• 128-bit compatibility with UUID
• 1.21e+24 unique ULIDs per millisecond
• Lexicographically sortable!
• Canonically encoded as a 26 character string, as opposed to the 36 character UUID
• Uses Crockford’s base32 for better efficiency and readability (5 bits per character)
• Case insensitive
• No special characters (URL safe)
• Monotonic sort order (correctly detects and handles the same millisecond)

Import

import { ulid } from "https://deno.land/x/ulid@v0.2.0/mod.ts";

Usage

To generate a ULID, simply run the function:

import { ulid } from "https://deno.land/x/ulid@v0.2.0/mod.ts";

ulid(); // 01ARZ3NDEKTSV4RRFFQ69G5FAV

Seed Time

You can also input a seed time which will consistently give you the same string for the time component. This is useful for migrating to ulid.

ulid(1469918176385); // 01ARYZ6S41TSV4RRFFQ69G5FAV

Monotonic ULIDs

To generate monotonically increasing ULIDs, create a monotonic counter.

Note that the same seed time is being passed in for this example to demonstrate its behaviour when generating multiple ULIDs within the same millisecond

import { monotonicFactory } from "https://deno.land/x/ulid@v0.2.0/mod.ts";

const ulid = monotonicFactory();

// Strict ordering for the same timestamp, by incrementing the least-significant random bit by 1
ulid(150000); // 000XAL6S41ACTAV9WEVGEMMVR8
ulid(150000); // 000XAL6S41ACTAV9WEVGEMMVR9
ulid(150000); // 000XAL6S41ACTAV9WEVGEMMVRA
ulid(150000); // 000XAL6S41ACTAV9WEVGEMMVRB
ulid(150000); // 000XAL6S41ACTAV9WEVGEMMVRC

// Even if a lower timestamp is passed (or generated), it will preserve sort order
ulid(100000); // 000XAL6S41ACTAV9WEVGEMMVRD

Use your own PRNG

To use your own pseudo-random number generator, import the factory, and pass it your generator function.

import { factory } from "https://deno.land/x/ulid@v0.2.0/mod.ts";
import prng from "somewhere";

const ulid = factory(prng);

ulid(); // 01BXAVRG61YJ5YSBRM51702F6M

You can also pass in a prng to the monotonicFactory function.

import { monotonicFactory } from "https://deno.land/x/ulid@v0.2.0/mod.ts";
import prng from "somewhere";

const ulid = monotonicFactory(prng);

ulid(); // 01BXAVRG61YJ5YSBRM51702F6M

Implementations in other languages

Refer to ulid/spec

Specification

Refer to ulid/spec

Test Suite

deno test

Performance

deno bench

cpu: Apple M1
runtime: deno 1.34.1 (aarch64-apple-darwin)

file:///Users/kt3k/oss/ulid/bench.ts
benchmark         time (avg)             (min … max)       p75       p99      p995
---------------------------------------------------- -----------------------------
encodeTime    378.13 ns/iter(324.22 ns … 432.38 ns) 387.6 ns 418.98 ns 432.38 ns
encodeRandom  1.72 µs/iter(1.68 µs … 1.79 µs) 1.74 µs 1.79 µs 1.79 µs
generate      3.08 µs/iter(3.03 µs … 3.32 µs) 3.07 µs 3.32 µs 3.32 µs