fisher-shuffle

fisher-shuffle

A set of utility functions to shuffle and generate random array sequences based on Fisher–Yates Algorithm. The package is written in typescript and does not depend on any other packages. The package is published as an npm module.

New : Introducing custom shuffle function :

Fisher shuffle works by generating random indexes i and j upon every iteration, it then swaps array[i] and array[j] to randomize the array, functions like shuffleArrayInPlace and shuffleArray are designed based on this principle, But not all uses-cases that require shuffling can be represented as arrays. For example, some applications in Grahpics usually make use of custom non-array objects like HTML5 canvas which can manipulate pixel level data, in order to shuffle pixels, one may have to copy those to an array, call shuffleArrayInPlace and then populate the canvas back with randomized points, which can be time-consuming, to deal with such tasks, we are introducing shuffleCustom function, which allows you to write your own swapping operation, the function will be called for every iteration of the loop and will be provided with random i and j indexes as parameters, you can write your own swapping logic given i and j, (in the example we discussed, you can just get and set pixels for i and j indexes, which is more efficient, than re-populating the entire canvas). See the example below to understand how to use shuffleCustom :

const randomUtils = require('fisher-shuffle')
 
const array = [1,2,3,4,5,6]
 
//this is your custom shuffle function, you can write any logic or manipulate any object according to i and j indexes
var customFunction = (i, j) => {
    const temp = array[i];
    array[i] = array[j];
    array[j] = temp;
}
 
randomUtils.shuffleCustom(customFunction, array.length);
console.log(array)

1. To install :

npm install fisher-shuffle

2. Functions

a. shuffleArray : Creates a new array which is the shuffled version of the old one, (note : this creates another array in memory)

const randomUtils = require('fisher-shuffle')
 
//It can shuffle arrays of any type. (including custom object arrays)
const originalArray = [1,2,3,4,5,6,7, 8, 9, 10]
const shuffledArray = randomUtils.shuffleArray(originalArray)
 
console.log(shuffledArray)
 
//output : [10, 9, 5, 7, 1, 2, 6, 4, 8, 3]

b. shuffleArrayInPlace : This function shuffles the array in-place without creating another array in O(n) time. This is the best method to use to shuffle large arrays, which are memory-costly.

const randomUtils = require('fisher-shuffle')
 
//It can shuffle arrays of any type. (including custom object arrays)
const originalArray = [1,2,3,4,5,6,7, 8, 9, 10]
randomUtils.shuffleArrayInPlace(originalArray)
 
console.log(originalArray)
 
//output : [4, 5,  9, 2, 7, 3, 6, 10, 8, 1 ]

c. generateSequence : Generates a linear sequence from min to max by incrementing step every time, this is just like python's range, except the returns the array at once.

const randomUtils = require('fisher-shuffle')
 
//It can generate integer and floating point sequences
const result = randomUtils.generateSequence(min = 0, max = 100, step = 10)
console.log(result)
 
//output : [0, 10, 20, 30, 40, 50, 60, 70, 80, 90]

d. generateRandomSequence : Generates a random sequence between the range min and max, with step difference. The result is a unique sequence, which means there are no repetitions.

const randomUtils = require('fisher-shuffle')
 
//It can generate integer and floating point sequences
const result = randomUtils.generateRandomSequence(min = 0, max = 100, step = 10)
console.log(result)
 
//output : [40, 50,  0, 60, 10,90, 30, 80, 70, 20]

3. Development :

As a developer, if you want to develop modules on top of fisher-shuffle or modify the codebase, you have to setup the development environment. The project is written using typescript, version 4.0.3. You can simply run npm install to install typescript.

a. Compiling :

To compile the module, run :

npm run build

or you can use tsc if typescript is installed globally.

b. Running unit-tests :

We are using mocha and chai to write unit-tests. Run npm install and npm run test to run the unit-tests.

Checkout tests/index.test.js to see unit-tests.

To run the test suite, run :

npm run test

4. Contributing

Contributions are welcome. You can add new functionalities or write tests. We are using mocha and chai for unit-testing.

We have added a github-action to build and execute unit-tests before merging any PR.

Acknowledements

1. Fisher–Yates algorithm