feat(string): adds support for generating ULID

src/internal/base32.ts

@@ -0,0 +1,21 @@
+/**
+ * Crockford's Base32 - Excludes I, L, O, and U which may be confused with numbers
+ */
+export const CROCKFORDS_BASE32 = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
+
+/**
+ * Encodes a Date into 10 characters base32 string.
+ *
+ * @param date The Date to encode.
+ */
+export function dateToBase32(date: Date): string {
+  let value = date.valueOf();
+  let result = '';
+  for (let len = 10; len > 0; len--) {
+    const mod = value % 32;
+    result = CROCKFORDS_BASE32[mod] + result;
+    value = (value - mod) / 32;
+  }
+
+  return result;
+}

src/internal/date.ts

@@ -0,0 +1,22 @@
+import { FakerError } from '../errors/faker-error';
+
+/**
+ * Converts a date passed as a `string`, `number` or `Date` to a valid `Date` object.
+ *
+ * @param date The date to convert.
+ * @param name The reference name used for error messages. Defaults to `'refDate'`.
+ *
+ * @throws If the given date is invalid.
+ */
+export function toDate(
+  date: string | Date | number,
+  name: string = 'refDate'
+): Date {
+  const converted = new Date(date);
+
+  if (Number.isNaN(converted.valueOf())) {
+    throw new FakerError(`Invalid ${name} date: ${date.toString()}`);
+  }
+
+  return converted;
+}

src/modules/date/index.ts

@@ -1,27 +1,10 @@
 import type { Faker } from '../..';
 import type { DateEntryDefinition } from '../../definitions';
 import { FakerError } from '../../errors/faker-error';
+import { toDate } from '../../internal/date';
 import { SimpleModuleBase } from '../../internal/module-base';
 import { assertLocaleData } from '../../locale-proxy';
 
-/**
- * Converts a date passed as a `string`, `number` or `Date` to a valid `Date` object.
- *
- * @param date The date to convert.
- * @param name The reference name used for error messages. Defaults to `'refDate'`.
- *
- * @throws If the given date is invalid.
- */
-function toDate(date: string | Date | number, name: string = 'refDate'): Date {
-  const converted = new Date(date);
-
-  if (Number.isNaN(converted.valueOf())) {
-    throw new FakerError(`Invalid ${name} date: ${date.toString()}`);
-  }
-
-  return converted;
-}
-
 /**
  * Module to generate dates (without methods requiring localized data).
  */

src/modules/string/index.ts

@@ -1,4 +1,6 @@
 import { FakerError } from '../../errors/faker-error';
+import { CROCKFORDS_BASE32, dateToBase32 } from '../../internal/base32';
+import { toDate } from '../../internal/date';
 import { SimpleModuleBase } from '../../internal/module-base';
 import type { LiteralUnion } from '../../utils/types';
 
@@ -704,6 +706,37 @@ export class StringModule extends SimpleModuleBase {
       .replaceAll('y', () => this.faker.number.hex({ min: 0x8, max: 0xb }));
   }
 
+  /**
+   * Returns a ULID ([Universally Unique Lexicographically Sortable Identifier](https://github.com/ulid/spec)).
+   *
+   * @param options The optional options object.
+   * @param options.refDate The timestamp to encode into the ULID.
+   * The encoded timestamp is represented by the first 10 characters of the result.
+   * Defaults to `faker.defaultRefDate()`.
+   *
+   * @example
+   * faker.string.ulid() // '01ARZ3NDEKTSV4RRFFQ69G5FAV'
+   * faker.string.ulid({ refDate: '2020-01-01T00:00:00.000Z' }) // '01DXF6DT00CX9QNNW7PNXQ3YR8'
+   *
+   * @since 9.1.0
+   */
+  ulid(
+    options: {
+      /**
+       * The date to use as reference point for the newly generated ULID encoded timestamp.
+       * The encoded timestamp is represented by the first 10 characters of the result.
+       *
+       * @default faker.defaultRefDate()
+       */
+      refDate?: string | Date | number;
+    } = {}
+  ): string {
+    const { refDate = this.faker.defaultRefDate() } = options;
+    const date = toDate(refDate);
+
+    return dateToBase32(date) + this.fromCharacters(CROCKFORDS_BASE32, 16);
+  }
+
   /**
    * Generates a [Nano ID](https://github.com/ai/nanoid).
    *

test/internal/__snapshots__/base32.spec.ts.snap

@@ -0,0 +1,3 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`dateToBase32() > encodes current date correctly 1`] = `"01GWX1T800"`;

test/internal/base32.spec.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+import { CROCKFORDS_BASE32, dateToBase32 } from '../../src/internal/base32';
+
+describe('dateToBase32()', () => {
+  it('encodes current date correctly', () => {
+    const date = new Date('2023-04-01T00:00:00Z');
+    const encoded = dateToBase32(date);
+    expect(encoded).toHaveLength(10);
+    expect(encoded).toMatchSnapshot();
+    for (const char of encoded) {
+      expect(CROCKFORDS_BASE32).toContain(char);
+    }
+  });
+
+  it('encodes epoch start date correctly', () => {
+    const date = new Date('1970-01-01T00:00:00Z');
+    const encoded = dateToBase32(date);
+    expect(encoded).toBe('0000000000');
+  });
+
+  it('returns different encodings for dates one millisecond apart', () => {
+    const date1 = new Date('2023-04-01T00:00:00.000Z');
+    const date2 = new Date('2023-04-01T00:00:00.001Z');
+    const encoded1 = dateToBase32(date1);
+    const encoded2 = dateToBase32(date2);
+    expect(encoded1).not.toBe(encoded2);
+  });
+
+  it('encodes same date consistently', () => {
+    const date = new Date('2023-04-01T00:00:00Z');
+    const encoded1 = dateToBase32(date);
+    const encoded2 = dateToBase32(date);
+    expect(encoded1).toBe(encoded2);
+  });
+});

test/internal/date.spec.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from 'vitest';
+import { FakerError } from '../../src';
+import { toDate } from '../../src/internal/date';
+
+describe('toDate()', () => {
+  it('should convert a string date to a valid Date object', () => {
+    const dateString = '2024-07-05';
+    expect(toDate(dateString)).toEqual(new Date(dateString));
+  });
+
+  it('should convert a string datetime to a valid Date object', () => {
+    const timestamp = '2024-07-05T15:49:19+0000';
+    expect(toDate(timestamp)).toEqual(new Date(timestamp));
+  });
+
+  it('should throw a FakerError for an invalid date string', () => {
+    const timestamp = 'aaaa-07-05T15:49:19+0000';
+    expect(() => toDate(timestamp)).toThrow(
+      new FakerError(`Invalid refDate date: ${timestamp}`)
+    );
+  });
+});

test/modules/__snapshots__/string.spec.ts.snap

@@ -164,6 +164,12 @@ exports[`string > 42 > symbol > with length parameter 5`] = `">%*,/"`;
 
 exports[`string > 42 > symbol > with length range 1`] = `"}\\>%%"\`>[!~_'&"`;
 
+exports[`string > 42 > ulid > with Date refDate 1`] = `"01EZ2S259ZBYQK441VKP0ZT655"`;
+
+exports[`string > 42 > ulid > with number refDate 1`] = `"01EZ2S259ZBYQK441VKP0ZT655"`;
+
+exports[`string > 42 > ulid > with string refDate 1`] = `"01EZ2S259ZBYQK441VKP0ZT655"`;
+
 exports[`string > 42 > uuid 1`] = `"5fb9220d-9b0f-4d32-a248-6492457c3890"`;
 
 exports[`string > 42 > uuid 2`] = `"21ffc41a-7170-4e4a-9488-2fcfe9e13056"`;
@@ -338,6 +344,12 @@ exports[`string > 1211 > symbol > with length parameter 5`] = `"~]-|<"`;
 
 exports[`string > 1211 > symbol > with length range 1`] = `"{(~@@],[_]?_.\`\`'=',~"`;
 
+exports[`string > 1211 > ulid > with Date refDate 1`] = `"01EZ2S259ZXW7ZNNRBPTRMTDVV"`;
+
+exports[`string > 1211 > ulid > with number refDate 1`] = `"01EZ2S259ZXW7ZNNRBPTRMTDVV"`;
+
+exports[`string > 1211 > ulid > with string refDate 1`] = `"01EZ2S259ZXW7ZNNRBPTRMTDVV"`;
+
 exports[`string > 1211 > uuid 1`] = `"ee3faac5-bdca-4d6d-9d39-35fc6e8f34b8"`;
 
 exports[`string > 1211 > uuid 2`] = `"d64428b2-b736-43d9-970b-2b4c8739d1d7"`;
@@ -512,6 +524,12 @@ exports[`string > 1337 > symbol > with length parameter 5`] = `"]'*@:"`;
 
 exports[`string > 1337 > symbol > with length range 1`] = `"&)/+;)~\\$-?%"`;
 
+exports[`string > 1337 > ulid > with Date refDate 1`] = `"01EZ2S259Z858EAG8ZQ3CM4ZES"`;
+
+exports[`string > 1337 > ulid > with number refDate 1`] = `"01EZ2S259Z858EAG8ZQ3CM4ZES"`;
+
+exports[`string > 1337 > ulid > with string refDate 1`] = `"01EZ2S259Z858EAG8ZQ3CM4ZES"`;
+
 exports[`string > 1337 > uuid 1`] = `"4247584f-b16a-42f7-8cc5-69c34a72638d"`;
 
 exports[`string > 1337 > uuid 2`] = `"f6880bf2-25b0-450c-a5b7-fd99f401ff75"`;

test/modules/string.spec.ts

@@ -113,6 +113,16 @@ describe('string', () => {
 
     t.itRepeated('uuid', 5);
 
+    t.describe('ulid', (t) => {
+      const ulidRefDate = '2021-02-21T17:09:15.711Z';
+
+      t.it('with string refDate', { refDate: ulidRefDate })
+        .it('with Date refDate', { refDate: new Date(ulidRefDate) })
+        .it('with number refDate', {
+          refDate: new Date(ulidRefDate).getTime(),
+        });
+    });
+
     t.describe('nanoid', (t) => {
       t.itRepeated('noArgs', 5)
         .it('with length parameter', 30)
@@ -750,6 +760,23 @@ describe('string', () => {
         });
       });
 
+      describe(`ulid`, () => {
+        it.each(['invalid', Number.NaN, new Date(Number.NaN)] as const)(
+          'should reject invalid refDates %s',
+          (refDate) => {
+            expect(() => faker.string.ulid({ refDate })).toThrow(
+              new FakerError(`Invalid refDate date: ${refDate.toString()}`)
+            );
+          }
+        );
+
+        it('generates a valid ULID', () => {
+          const ulid = faker.string.ulid();
+          const regex = /^[0-7][0-9A-HJKMNP-TV-Z]{25}$/;
+          expect(ulid).toMatch(regex);
+        });
+      });
+
       describe(`nanoid`, () => {
         it('generates a valid Nano ID', () => {
           const id = faker.string.nanoid();