ulid JavaScript

To use the ulid library in your project, install it using npm:

npm install ulid --save

Import the ulid function to generate a new, unique, lexicographically sortable 26-character identifier.

import { ulid } from "ulid";

ulid(); // "01ARZ3NDEKTSV4RRFFQ69G5FAV"

You can pass a millisecond timestamp as an argument to ulid(). This ensures the time component of the generated ULID remains consistent, which is useful for data migrations.

ulid(1469918176385) // "01ARYZ6S41TSV4RRFFQ69G5FAV"

By default, ulid uses cryptographically-secure PRNGs (crypto.getRandomValues in browsers or crypto.randomBytes in Node.js). If you need to use an insecure generator like Math.random, you can pass it to monotonicFactory.

const ulid = monotonicFactory(() => Math.random());

ulid(); // "01BXAVRG61YJ5YSBRM51702F6M"

Use the isValid function to check if a given string is a valid ULID.

import { isValid } from "ulid";

isValid("01ARYZ6S41TSV4RRFFQ69G5FAV"); // true
isValid("01ARYZ6S41TSV4RRFFQ69G5FA"); // false

To ensure that ULIDs generated within the same millisecond maintain a strict sort order, use monotonicFactory. This increments the least-significant random bits for subsequent calls within the same timestamp, and preserves sort order even if a lower timestamp is provided later.

import { monotonicFactory } from "ulid";

const ulid = monotonicFactory();

// Strict ordering for the same timestamp
ulid(150000); // "000XAL6S41ACTAV9WEVGEMMVR8"
ulid(150000); // "000XAL6S41ACTAV9WEVGEMMVR9"

// Preserves sort order even with a lower timestamp
ulid(100000); // "000XAL6S41ACTAV9WEVGEMMVRD"

You can extract the timestamp from a ULID using decodeTime, or create a ULID time component string using encodeTime.

Note: encodeTime only encodes the time portion (the first 10 characters) of a ULID, not a full 26-character ID.