@lou.codes/iterables/dist/asynchronous/random.js

🔁 Iterable and AsyncIterable utils

import { cryptoNumber } from "@lou.codes/utils";
import { createIterableIterator } from "./createIterableIterator.js";
/**
 * Deterministic pseudo-random number generator.
 *
 * **⚠️ IMPORTANT:** This only works in secure contexts (HTTPS/Node).
 *
 * @category Asynchronous Generators
 * @example
 * ```typescript
 * const seededRandom = random("some seed");
 * const random0To10 = seededRandom(0)(10);
 *
 * [...pick(2)(random0To10)]; // Two "random" values between 0 and 10
 * [...pick(2)(random0To10)]; // Same two "random" values between 0 and 10
 * ```
 * @see [SubtleCrypto#digest](https://mdn.io/SubtleCrypto.digest)
 * @see [cryptoNumber](https://lou.codes/libraries/lou_codes_utils/#cryptonumber)
 * @param seed Seed to be used to generate random numbers.
 * @returns Curried generator function with `seed` set in context.
 */
export const random = seed => from => to =>
	createIterableIterator(async function* () {
		let state = seed;
		const min = from < to ? from : to;
		const max = from > to ? from : to;
		// eslint-disable-next-line functional/no-loop-statements
		for (;;) {
			yield Math.min(
				Math.max(
					(state =
						(await cryptoNumber(`${state}(${min}-${max})`)) *
							(max + 2 - min) +
						(min - 1)),
					min,
				),
				max,
			);
		}
	});