// Copyright 2018-2025 the Deno authors. MIT license.
// Copyright 2023 Yoshiya Hinosawa. All rights reserved. MIT license.
// Copyright 2017 Alizain Feerasta. All rights reserved. MIT license.
// This module is browser compatible.
import { encodeRandom, encodeTime } from "./_util.ts";
/**
* Generate a ULID, optionally based on a given timestamp. If the timestamp is
* not passed, it will default to `Date.now()`.
*
* Multiple calls to this function with the same seed time will not guarantee
* that the ULIDs will be strictly increasing, even if the seed time is the
* same. For that, use the {@linkcode monotonicUlid} function.
*
* @example Generate a ULID
* ```ts no-assert
* import { ulid } from "@std/ulid";
*
* ulid(); // 01HYFKMDF3HVJ4J3JZW8KXPVTY
* ulid(); // 01HYFKMDF3D2P7G502B9Z2VKV0
* ulid(); // 01HYFKMDZQ7JD17CRKDXQSZ3Z4
* ```
*
* @example Generate a ULID with a seed time
* ```ts no-assert
* import { ulid } from "@std/ulid";
*
* ulid(150000); // 0000004JFG3EKDRE04TVVDJW7K
* ulid(150000); // 0000004JFGN0KHBH0447AK895X
* ulid(150000); // 0000004JFGMRDH0PN7SM8BZN06
* ```
*
* @param seedTime The time to base the ULID on, in milliseconds since the Unix epoch. Defaults to `Date.now()`.
* @returns A ULID.
*/
export function ulid(seedTime: number = Date.now()): string {
return encodeTime(seedTime) + encodeRandom();
}
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