rpg-dice-roller

A basic JS based dice roller that accepts typical dice notation.

Supported notation

The standard notation formats are accepted, such as 2d6+12, and also the use of L or H to represent the lowest or highest roll respectively.
ie. 4d6-L (A roll of 4 six-sided dice, dropping the lowest result)

Operators

You can also use multiply and divide mathematical operators; 1d6*5 or 2d10/d20.

Percentile dice (d%)

Although percentile dice can be rolled by using a d100, you can also use d%, which will do the same thing, returning a number between 0 and 100.

Exploding dice

Exploding dice roll an additional die if the maximum, on that die, is rolled. If that die is also the maximum it is rolled again, and so forth, until a roll is made that isn't the maximum.
ie. Rolling a 6 on a d6, or a 10 on a d10.

To explode a dice, add an exclamation mark after the die sides: 4d10!

Each exploded die shows as a separate roll in the list, like so:

2d6!: [4, 6!, 6!, 2] = 20

Where the second roll exploded, so we rolled again, which also exploded. The fourth role, however, did not, so we stop rolling.

You can even use L and H, which will look at exploded dice, as well as normal rolls.
i.e.

1d6!-L: [6!,6!,6!,3]-L = 18

Compounding

Sometimes, you may want the exploded dice rolls to be added together under the same, original roll. In this situation, you can compound the dice by using two exclamation marks: 4d10!!

For example (using the examples of exploding dice above):

2d6!!: [4, 14!!] = 20   // the exploded dice rolls of [6, 6, 2] are added together
1d6!!-L: [21!!]-L = 18  // the exploded dice rolls of [6, 6, 6, 3] are added together

Penetrating

Some exploding dice system use a penetrating rule.

Taken from the Hackmaster Basic rules:

Should you roll the maximum value on this particular die, you may re-roll and add the result of the extra die, less one point, to the total (penetration can actually result in simply the maximum die value if a 1 is subsequently rolled, since any fool knows that 1-1=0). This process continues indefinitely as long as the die in question continues to come up maximum (but there’s always only a –1 subtracted from the extra die, even if it’s, say, the third die of penetration)

So, if I rolled 1d6 (penetrating), and got a 6, I would roll another d6, subtracting 1 from the result. If that d6 rolled a 6 (before the -1) it would penetrate, and so on.

The syntax for penetrating is very similar to exploding, but with a lowercase 'p' appended: 2d6!p.
i.e. (Using the same example from exploding dice above):

2d6!p: [4, 6!p, 5, 1] = 20

Where the second roll exploded, so we rolled again, which also exploded (rolled a 6). The fourth role, however, rolled a 2, so did not penetrate, so we stop rolling.
Remember that we subtract 1 from penetrated rolls, which is why we show '5' and '1', instead of '6', and '2'.

You can also compound penetrating dice, like so: 2d6!!p

Compare point

By default, Exploding and penetrating dice do so if you roll the highest number possible on the dice (ie. a 6 on a d6, a 1 on a Fudge die).
You can easily change the exploding compare point by adding a comparison after it. ie. to explode only if you roll a 4:

2d6!=4

Or exploding if you roll anything over a 4:

2d6!>4

You can also use this with penetrating and compounding dice:

2d6!!<=4  // compound if you roll a 4 or lower
2d6!p!=4  // penetrate if you *don't* roll a 4

There is an obvious issue here, wherein you can't do a normal explode if you don't roll a certain number. ie:

2d6!!=4

This will actually tell it to compound if you roll a 4. Solutions are currently being looked in to.

Fudge dice

Fudge notation is also supported. It allows both dF.2 and less common dF.1.

You can also use it in conjunction with other operators.

Examples:

dF      // this is the same as `dF.2`
4dF.2   // roll 4 standard fudge dice
4dF.2-L // roll 4 standard fudge dice, subtracting the lowest result
dF.1*2  // roll non-standard fudge dice, multiplying the result by 2

Dice pools

Some systems use dice pool, whereby the total is equal to the number of dice rolled that meet a fixed condition, rather than the total value of the rolls.

For example, a "pool" of 10 sided dice where you count the number of dice that roll an 8 or higher as "successes".
This can be achieved with:

5d10>=8

You can define various success conditions, by simply adding number comparisons directly after the dice roll.
Because of this, you can not have a pool dice that also explodes.

Examples:

2d6=6: [4,6*] = 1               // only a roll of 6 is a success
4d3>1: [1,3*,2*,1] = 2          // higher than a 1 is a success
4d3<2: [1*,3,2,1*] = 2          // lower than a 2 is a success
5d8>=5: [2,4,6*,3,8*] = 2       // higher than or equal to 5 is a success
6d10<=4: [7,2*,10,3*,3*,4*] = 4 // less than or equal to 4 is a success

You can mix pool dice with other dice types or equations, and it will use the number of successes as the value in the equation:

2d6>4+3d5: [4,5*]+[3,1,1] = 6   // 1 success + the raw values of the other rolls
2d6>4*d6!: [6*,5*]*[6!,4] = 20  // 2 successes * raw values of the other rolls
2d6>4+2: [3,5*]+2 = 3           // 1 success + 2
2d6>4+H: [3,5*]+H = 2           // Highest roll is 5, which is a success, so `H` has a value of 1
2d6<4+H: [3*,5]+H = 1           // Highest roll is 5, which is a failure, so `H` has a value of 0

The successes property on the DiceRoll object will provide the number of successes for a roll.
However, if the roll is just dice pool, and does not contain any other operations, or dice rolls, then the value provided will be the same as the totals property.

Maths

Parenthesis are recognised anywhere in notations to group sections and define the order of operations:

1d6+2*3: [4]+2*3 = 10
(1d6+2)*3: ([4]+2)*3 = 18

You can also use an array of mathematical formulas and functions. Internally it uses Math.Js, so you should be able to use any of its built in arithmetic functions.

Some examples:

round(4d10/3): round([3,6,1,1]/3) = 3.7  // round the result to the nearest whole number
floor(4d10/3): round([3,6,1,1]/3) = 3.6  // round the result down to the nearest whole number
ceil(4d10/3): round([3,6,1,1]/3) = 3.7   // round the result up to the nearest whole number

Get Started

Setup

Install through:

• NPM:

  $ npm install rpg-dice-roller

• Yarn:

  yarn add rpg-dice-roller

• CDN

  <script src="https://cdn.jsdelivr.net/npm/rpg-dice-roller@VERSION/lib/umd/bundle.min.js"></script>

Usage

• Using NodeJS/commonJS/AMD etc.? check the NodeJS section.
• No ES6 module support? read the Older Browsers section below.

You can import the dice roller and use it in your application, using ES standard modules like so:

// import only the DiceRoller class
import { DiceRoller } from 'lib/esm/bundle.min.js';

// create a new instance of the DiceRoller
const roller = new DiceRoller();

// roll the dice
roller.roll('4d20-L');

// get the latest dice rolls from the log
let latestRoll = roller.log.shift();

// output the latest roll - it has a toString method for nice output when converted to a string
document.write(latestRoll);


// roll several notations all at once, and store their DiceRoll objects
const rolls = roller.rollMany(['1d6', '2d4-H', '5d10!!']);

If you need to manually create DiceRoll objects, you need to import the module:

// import the DiceRoller and DiceRoll classes
import { DiceRoller, DiceRoll } from 'lib/esm/bundle.min.js';

// roll a single notation without saving it to the log
const diceRoll = new DiceRoll('2d6-L');

// export the dice roll as JSON
let exportedData = diceRoll.export(exportFormats.JSON);

// we can also import data either from a previous export, or built up manually
// Note that here we're calling `import` on the `DiceRoll` class, not an existing object
let importedDiceRoll = DiceRoll.import(exportedData);


// importing into a DiceRoller is just as easy
const roller = new DiceRoller();
roller.import(exportedData); // appends roll data to the end of existing roll log

// creates a new DiceRoller and stores the roll data
const roller2 = DiceRoller.import(exportedData);

Rather than specifying the individual components, you can import everything like so:

// import the everything and store on the `rpgDiceRoller` scope
import * as rpgDiceRoller from 'lib/esm/bundle.min.js';

// create a DiceRoller
const roller = new rpgDiceRoller.DiceRoller();

// create a DiceRoll
const roll = new rpgDiceRoller.DiceRoll('2d6');

NodeJS And Module Loaders

You can also load the library using CommonJS, AMD, etc.

Instead of the lib/esm/bundle.min.js file, node should use the lib/umd/bundle.min.js file, as defined in the package.json main property.

Here is an example in Node.js:

// require the dice-roller library
const { DiceRoller } = require('rpg-dice-roller');

// create a new instance of the DiceRoller
const diceRoller = new DiceRoller();

// roll the dice
diceRoller.roll('4d20-L');

// get the latest dice rolls from the log
let latestRoll = diceRoller.log.shift();

// output the latest roll - it has a toString method for nice output
console.log(latestRoll + '');

Older Browsers

We support some older browsers without ES6 or native Module support.

Instead of the lib/esm/bundle.min.js file, you must use the lib/umd/bundle.min.js file.

All uses of the library classes and objects must be accessed from the rpgDiceRoller namespace.

<script src="lib/umd/bundle.min.js"></script>
<script>
  // create a new instance of the DiceRoller
  var diceRoller = new rpgDiceRoller.DiceRoller();

  // roll the dice
  diceRoller.roll('4d20-L');
  
  // create a new instance of a DiceRoll
  var diceRoll = new rpgDiceRoller.DiceRoll('2d6');
</script>

API

The Dice Roller provides a DiceRoller class, of which you can have multiple instances:

// my first DiceRoller
const roller1 = new DiceRoller();

// my second DiceRoller
const roller2 = new DiceRoller();

Each instance keeps it's own log of dice rolls, so it's handy if you're rolling for several completely unrelated things.

DiceRoller object

Static properties

Static properties can be called on the class itself, without instantiating an object, like so:

const diceRoller = DiceRoller.import(data); // returns a new DiceRoller instance with the given data

DiceRoll object

A DiceRoll object takes a notation and parses it in to rolls.

It can be created like so:

const roll = new DiceRoll('4d10');

Static properties

Static properties can be called on the class itself, without instantiating an object, like so:

const diceRoll = DiceRoll.import(data);

Browser support

This dice roller uses modern JS and native JS modules, which work in all the latest browsers.

• For older browsers check out the Older Browsers section.
  Note: This library is built with a modern approach and will not work in all older browsers
• For NodeJs check out the NodeJS

Demo

View the demo here: http://rpg.greenimp.co.uk/dice-roller

Licence

This dice roller is released under the MIT licence, meaning that you can do pretty much anything you like with it, so long as the original copyright remains in place.

You can use it in commercial products.

If the licence terminology in the licence.txt is confusing, check out this: https://www.tldrlegal.com/l/mit

Reference

Further information on the basic dice notation can be found here: https://en.wikipedia.org/wiki/Dice_notation