jsrand a.k.a. seeded-rand

A seeded pseudo-random number generator for JavaScript.

It can be used as either a plain script or as a Node.js module.

Numbers are generated using a one-seeded version of the multiply-with-carry method by George Marsaglia. While this method is okay for most applications, it is not cryptographically strong.

jsrand supports saving and restoring the generator state and common operations on arrays: choice (pick a random element), choices (pick elements at random), sample (pick elements at random without repetition) and shuffle.

See changelog here.

Table of contents

• Install
  • NPM
  • Plain script
• Usage
  • Examples
• API
  • choice
  • choices
  • getState
  • inRange
  • intInRange
  • noConflict
  • random
  • randomize
  • sample
  • seed
  • setState
  • shuffle
• License

Install

NPM

$ npm install seeded-rand

Plain script

Just download dist/jsrand.min.js and (optionally) dist/jsrand.min.js.map and include it in your app.

Usage

Plain script	NPM
<script src="jsrand.min.js"></script> This will define a global Srand object. If the name Srand is already taken, see noConflict.	const Srand = require('seeded-rand'); or import Srand from 'seeded-rand';

All methods can be used either statically:

Srand.seed(10); // 10
Srand.random(); // 0.4569510892033577

or instantiating a new generator:

const rnd = new Srand(10);
rnd.random(); // 0.4569510892033577

const othr = new Srand(rnd.seed());
othr.random(); // 0.4569510892033577

Examples

const rnd = new Srand(); // Initiate with random seed

rnd.seed(); // 1836504610 Read the seed
rnd.randomize(); // 3409024789 Random seed is set and returned
rnd.seed(1836504610); // 1836504610 Set a seed

rnd.inRange(0, 10); // 6.866552880965173
rnd.intInRange(0, 10); // 1

rnd.choice([1, 2, 3]); // 3
rnd.choices([1, 2, 3], 3); // [3, 3, 1] possible repetitions
rnd.choices([1, 2, 3], 3); // [2, 2, 3] possible repetitions

rnd.sample([1, 2, 3], 2); // [1, 2] no repetitions
rnd.sample([1, 2, 3], 2); // [1, 2] no repetitions

const state = rnd.getState();
rnd.intInRange(1, 50); // 39
rnd.intInRange(1, 50); // 24
rnd.intInRange(1, 50); // 18

rnd.setState(state); // Resumes previous state, regenerating same random sequence
rnd.intInRange(1, 50); // 39
rnd.intInRange(1, 50); // 24
rnd.intInRange(1, 50); // 18

The same sequence of operations can be repeated with equal results using the static methods of Srand:

Srand.seed(1836504610); // 1836504610 Set the seed 

Srand.inRange(0, 10); // 6.866552880965173
Srand.intInRange(0, 10); // 1

Srand.choice([1, 2, 3]); // 3
Srand.choices([1, 2, 3], 3); // [3, 3, 1] possible repetitions
Srand.choices([1, 2, 3], 3); // [2, 2, 3] possible repetitions

Srand.sample([1, 2, 3], 2); // [1, 2] no repetitions
Srand.sample([1, 2, 3], 2); // [1, 2] no repetitions

const state = Srand.getState();
Srand.intInRange(1, 50); // 39
Srand.intInRange(1, 50); // 24
Srand.intInRange(1, 50); // 18

Srand.setState(state); // Resumes previous state, regenerating same random sequence
Srand.intInRange(1, 50); // 39
Srand.intInRange(1, 50); // 24
Srand.intInRange(1, 50); // 18

API

Method	Doc
choice(arr: Array<T>): T	Returns a random element from arr. If arr is empty, an exception is thrown.
choices(arr: Array<T>, k: number): Array<T>	Returns a k-sized array sampled with replacement from arr, i.e. each element can be sampled more than once. If k > 0 and arr is empty, throws an exception. For an alternative without replacement, see sample.
getState(): State	Returns an object with the state of the generator. Use setState to resume the state.
inRange(a: number, b: number): number	Returns a pseudo-random float number between a inclusive and b exclusive.
intInRange(min: number, max: number): number	Returns a psuedo-random integer between min and max inclusive.
noConflict(): Srand	Only available when using Srand as a plain script. In the uncommon case the name Srand is already taken, restores its initial value and return the Srand object. Srand = "my value"; // .. jsrand is loaded ... const mySrand = Srand.noConflict(); Srand; // "my value"
random(): number	Returns a pseudo-random float number between 0 inclusive and 1 exclusive. The algorithm used is a one-seeded version of the multiply-with-carry method by George Marsaglia.
randomize(): number	Sets and returns a random seed.
sample(arr: Array<T>, k: number): Array<T>	Returns a k-sized array sampled without replacement from arr. If k > arr.length, an exception is thrown. For an alternative with replacement, see choices.
seed(seed?: number): number	Sets or gets (if no argument is given) the seed. The seed can be any float or integer number.
setState(state: State): void	Resume a state previously returned by getState.
shuffle(arr: Array<T>): Array<T>	Shuffles arr in-place using the Fisher-Yates algorithm and returns it (arr is modified).

License

Copyright © 2014-2020, Domenico De Felice.

Provided under the terms of the MIT License.