dicekit-fp

A functional-programming-friendly library for rolling virtual dice. It provides pure-functional way to create random numbers and dice (functions that create random integers), combine and modiify the dice results, and convert strings like "2d6+2" to functions. It has no dependencies and is about 2KB minified.

Instead of using objects, the library creates random number generators based on the parameters you provide. The library uses higher-order functions to modify the results in order to modify or multiply the results of the dice rolls. Most of the functions return a () => number (aliased in the Typescript code as NumberGenerator).

The functions that produce random numbers, such as createDie(), typicially have two versions: one that takes a random number generator (RNG) as the first parameter and have the suffix With as in createDieWith(), the other which is already seeded with Math.random() as the RNG as in createDie()

Use

Create a basic die with createDie()

// takes a number of faces for the die as an argument and returns a function that generates ints.
const d6 = createDie(6);

// random int between 1 and 6
d6();

You can use any number (>=2) of faces

const coinFlip = createDie(2);
const devilDie = createDie(666);

Create multiple dice with a modifier in one step using createDice()

// takes a number of faces, number of dice (default 1), and modifier (default +0)
// 2d6+3
const _2d6plus3 = createDice(6, 2, 3);

// Random result of rolling 2 six sided dice and adding 3 to the result.
// (1..6) + (1..6) + 3
_2d6plus3();
// Note, this is not the same as a random int between 5..15.
// Because each die gets rolled independently, the results are more likely to follow a normal distribution curve favoring the middle numbers (like 7) more than the edge numbers (like 2 and 12)

// 2d6+0
const _2d6 = createDice(6, 2);
// 1d6+0
const _1d6 = createDice(6);

Combine multiple dice functions with combineDice()

const d6 = createDie(6);
const d8 = createDie(8);
// always returns 2
const two = () => 2;

// 2d6+1d8+2
const _2d6_1d8_2 = combineDice([d6, d6, d8, two]);

// generate random int
// (1..6) + (1..6) + (1..8) + 2
_2d6_1d8_2();

Dice Strings

Using parseDiceString(s) will convert a string into a function that rolls dice based on the input. The format of the string is inspired by Tabletop RPG dice notation.

${multiplier}d${sides}+${modifier}

Where:

• multiplier is the number of dice (default is 1)
• Use d or D to separate the multiplier from the number of sides on the dice.
• sides is the number of sides on the dice. The range will be 1 to sides, inclusive.
• modifier is an integer to add to the total

Examples

• "d6" -> roll one 6-sided-die`
• "2d6" -> roll two 6-sided-dice and sum results`
• "3d6+2" -> roll three 6-sided-dice, add 2 to the sum.`
• "2d12-2" -> roll two 12-sided-dice, subtract 2 from the sum.`
• "1d12-5+2d20+4+d4" -> roll one 12-sided-die, two 20-sided-dice, and one 4-sided-die, subtract 5 and add 4 to the sum.`

Whitespace and letter case are ignored.

Custom dice with createCustomDie()

To create a die that isn't typical, you can use createCustomDie() and provide an array of dice face values.

// Generate a random color string
const colors = ["red", "orange", "yellow", "green", "blue", "indigo", "violet"];
const colorDie = createCustomDie(colors);
colorDie(); // "blue"

// Create a die that lands on 6 more often.
const weightedD6 = createCustomDie([1, 2, 3, 4, 5, 6, 6, 6]);
weightedD6(); // 6, probably

// If the values are numerical, they can be combined with other dice functions...
const weightedDice = combineDice([weightedDie, weightedDie]);

Custom Random seed

All the fuctions that rely on a random number generator come with a version that uses Math.random for the RNG. To use a different generator, use the alternate versions with the suffix With as in createDieWith(f) where f is a function that takes no arguments and returns a number, n, where 0.0<=n<1.0

const myRNG = randomSeed.create("my seed");
const createDieSeeded = createDieWith(myRNG);

const d6 = createDieSeeded(6);
d6(); // uses myRNG for generating numbers.

Other functions

TBD. Meanwhile, please review test folder for examples.

Below this line is boilerplate from the template

=====

Vite npm package template

A template for an npm package using:

• vite
• typescript
• jest
• prettier & eslint
• controlled commits with commitizen, lint-staged, etc.
• & more!

Inspired by this post by Onur Önder

Setup

1. Install packages.
2. Edit the top of the package.json file to include the correct package name and description. You can find and replace for "<LIBRARY>"
3. Edit the README.md
4. You may need to review the vite.config.js depending on your library structure.

Scripts

• lint : lint the code. You can also do fix to auto-fix.
• test : test with jest. Also test:coverage and test:watch
• build : bundle the code
• commit & release : see below
• pushpub: Used after release it pushes and publishes the library.
• deploy: Build the demo code (index.html) and publish to gh-pages

Commits & Releases

Code is automatically linted before being committed. I recommend installing the plugins for eslint and prettier in your code editor. You can attempt to fix linting issues with yarn fix.

When ready to commit, please commit using yarn commit to use commitizen for standard format commits.

When ready to release use yarn release with the -r patch|minor|major flag (default without the flag is patch).

You'll then need to publish your changes separately. That can be done with yarn pushpub.

You can deploy an updated demo to github pages using yarn deploy