Randomizer

Interface for a random number generator.

Note: Normally there is no need to implement this interface directly, unless you want to achieve a specific goal with it.

This interface enables you to use random generators from third party libraries such as pure-rand.

Instances are expected to be ready for use before being passed to any Faker constructor, this includes being seed()ed with either a random or fixed value.

For more information please refer to the documentation.

import { Faker, Randomizer, SimpleFaker } from '@faker-js/faker';
import { RandomGenerator, xoroshiro128plus } from 'pure-rand';

function generatePureRandRandomizer(
  seed: number | number[] = Date.now() ^ (Math.random() * 0x100000000),
  factory: (seed: number) => RandomGenerator = xoroshiro128plus
): Randomizer {
  const self = {
    next: () => (self.generator.unsafeNext() >>> 0) / 0x100000000,
    seed: (seed: number | number[]) => {
      self.generator = factory(typeof seed === 'number' ? seed : seed[0]);
    },
  } as Randomizer & { generator: RandomGenerator };
  self.seed(seed);
  return self;
}

const randomizer = generatePureRandRandomizer();

const simpleFaker = new SimpleFaker({ randomizer });

const faker = new Faker({
  locale: ...,
  randomizer,
});

next

Generates a random float between 0 (inclusive) and 1 (exclusive).

Available since v8.2.0

Returns: number

randomizer.next(): number
randomizer.next() // 0.3404027920160495
randomizer.next() // 0.929890375900335
randomizer.next() // 0.5866362918861691

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seed

Sets the seed to use.

Available since v8.2.0

Parameters

Name	Type	Default	Description
seed	number | number[]		The seed to use.

Returns: void

randomizer.seed(seed: number | number[]): void
// Random seeds
randomizer.seed(Date.now() ^ (Math.random() * 0x100000000));
// Fixed seeds (for reproducibility)
randomizer.seed(42);
randomizer.seed([42, 13.37]);

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