DomenicoDeFelicejsrand 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.
Table of contents
Install
NPM
$ npm install seeded-randPlain 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(); // 0.4569510892033577or instantiating a new generator:
const rnd = new Srand(10);
rnd.random(); // 0.4569510892033577
const othr = new Srand(rnd.seed());
othr.random(); // 0.4569510892033577Examples
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); // 18The 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); // 18API
| 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
Copyright © 2014-2020, Domenico De Felice.
Provided under the terms of the MIT License.