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.

Install
- NPM
- Plain script
Usage
- Examples
API
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
`javascript <script src="jsrand.min.js"></script>` This will define a global `Srand` object. If the name `Srand` is already taken, see `noConflict`.	`javascript const Srand = require('seeded-rand');` or `Javascript 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
`Javascript choice(arr: Array<T>): T`	Returns a random element from `arr`. If `arr` is empty, an exception is thrown.
`Javascript 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`.
`Javascript getState(): State`	Returns an object with the state of the generator. Use `setState` to resume the state.
`Javascript inRange(a: number, b: number): number`	Returns a pseudo-random float number between `a` inclusive and `b` exclusive.
`Javascript intInRange(min: number, max: number): number`	Returns a psuedo-random integer between `min` and `max` inclusive.
`Javascript 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. `javascript Srand = "my value"; // .. jsrand is loaded ... const mySrand = Srand.noConflict(); Srand; // "my value"`
`Javascript 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.
`Javascript randomize(): number`	Sets and returns a random seed.
`Javascript 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`.
`Javascript seed(seed?: number): number`	Sets or gets (if no argument is given) the seed. The seed can be any float or integer number.
`Javascript setState(state: State): void`	Resume a state previously returned by `getState`.
`Javascript shuffle(arr: Array<T>): Array<T>`	Shuffles `arr` in-place using the Fisher-Yates algorithm and returns it (`arr` is modified).

License

Provided under the terms of the MIT License.