@3d-dice/dice-roller-parser
v0.2.6
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A javascript dice roller that parses roll20 format strings and generates rolled outputs
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Dice Roller & Parser
This dice roller is a string parser that returns an object containing the component parts of the dice roll. It supports the full Roll20 Dice Specification. It uses a pegjs grammar to create a representation of the dice roll format. This can then be converted into a simple number value, or to a complex object used to display the full roll details.
Credit
This is a fork of Ben Morton's dice_roller project. It had a few bugs so I'm republishing with fixes and features needed for my projects.
Quickstart
Install the library using:
npm install dice-roller-parser
Once installed, simply load the library, either in the browser:
<script src="node_modules/dice-roller-parser/dist/index.js"></script>
Or in node:
import { DiceRoller } from "dice-roller-parser";
Then create a new instance of the DiceRoller
class, and use it to perform some dice rolls.
const diceRoller = new DiceRoller();
// Returns the total rolled value
const roll = diceRoller.rollValue("2d20kh1");
console.log(roll);
// Returns an object representing the dice roll, use to display the component parts of the roll
const rollObject = diceRoller.roll("2d20kh1");
console.log(rollObject.value);
Usage
This library exposes two classes, a DiceRoller
and a DiscordRollRenderer
.
DiceRoller
The DiceRoller
class manages parsing of a dice string and performing rolls based upon the result.
// Creates a new instance of the DiceRoller class
const roller = new DiceRoller();
Constructor options
The default constructor uses Math.random
and applies a maximum number of rolls per die of 1000. These can be specified using the following constructor overloads.
DiceRoller(GeneratorFunction)
You can specify a function to be used as the random number generator by the dice roller. This function should be of the type () => number
and return a number between 0 and 1. By default, it uses the built-in Math.random
method.
// Default constructor using Math.random
const roller = new DiceRoller();
// Uses a custom random generator that always returns 0.5
const roller = new DiceRoller(() => 0.5);
This can be read or modified using the randFunction
property.
roller.randFunction = () => 0.5;
DiceRoller(GeneratorFunction, MaxRollsPerDie)
To prevent attempting to parse very large numbers of die rolls, a maximum number of rolls for a die can be specified. The default value is set to 1000.
// Uses the default constructor with a limit of 100 rolls per die
const roller = new DiceRoller(null, 100);
// Uses a custom random generator that always returns 0.5, and a limit of 10 rolls per die
const roller = new DiceRoller(() => 0.5, 10);
This can be read or modified using the maxRollCount
property.
roller.maxRollCount = 75;
Class Usage
Once the DiceRoller
class has been constructed, there are three options for performing a dice roll:
- Getting a roll result directly
- Generate an object to represent the dice roll
- Just parse the input and add your own rolling logic
Getting a direct roll result
The rollValue
method takes a dice string input, parses it, performs a roll and returns the calculated number value result.
// Rolls 2 d20 dice and keeps the value of the highest
const roll = roller.rollValue("2d20kh1");
// Prints out the numeric value result
console.log(roll);
Generate an object representing the dice roll
The roll
method takes a dice string input, parses it, performs a roll and then returns an object that represents the roll. Using the roll objects, you can build your own roll display functionality, rather than just outputting the final value.
// Rolls 2 d20 dice and keeps the value of the highest
const roll = roller.roll("2d20kh1");
// Print out the full roll breakdown
printDiceRoll(roll);
// Prints out the numeric value result
console.log(`Final roll value: ${roll.Value}`);
See the roll result output in the output types section below for more details on the returned object.
Just parse the value
The parse
method takes a dice string input, parses it and returns a representation of the parsed input. This can either be used to perform a dice roll or re-construct the original input. The rollParsed
method takes this parsed result as an input, performs the roll and returns the same output as from the roll
method.
// Rolls 2 d20 dice and keeps the value of the highest
const parsedInput = roller.parse("2d20kh1");
// Print out a re-constructed input string
printParsedInput(parsedInput);
// Run the roller on the parsed object
const roll = roller.rollParsed(parsedInput);
// Print out the full roll breakdown
printDiceRoll(roll);
// Print out the numeric value result
console.log(`Final roll value: ${roll.Value}`);
See the parsed roll output in the output types section below for more details on the returned object.
DiscordRollRenderer
The DiscordRollRenderer
class is an example renderer class that takes a rolled input represented by a RollBase
object and renders it to a string in a markdown format, compatible with Discord.
// Creates a new instance of the DiceRoller class
const renderer = new DiscordRollRenderer();
Class Usage
The DiscordRollRenderer
exposes a single render
method with a single parameter, the RollBase
object to render, and returns the rendered string.
// Rolls 2 d20 dice and keeps the value of the highest
const roll = roller.rollValue("2d20kh1");
// Get the formatted string
const render = renderer.render(roll);
console.log(render);
Development
To develop this library, simply clone the repository, run an install:
npm install
Then do a build:
npm run build
This does four things:
# Clean any existing builds
npm run clean
# Build the dice grammer
npx pegjs src/diceroll.pegjs
# Run tslint against the project
tslint -c tslint.json --project tsconfig.json
# Then run webpack to build and package everything up nicely
webpack
To run the test suite, use:
npm run test
That's all there is to it!
Output Types
The following object types are output from the DiceRoller
class, and are available as interfaces for typescript users.
Roll Result Output
The object returned by a roll result is made up of the following types.
RollBase
The base class for all die rolls, extended based upon the type property.
| Property | Type | Description |
| -------- | ----------------------- | ------------------------------------------------------------------- |
| success | boolean
| Was the roll a success, for target number rolls. Example: 3d6 > 3
|
| type | RollType
| The type of roll that this object represents. |
| valid | boolean
| Is the roll still valid, and included in calculations. |
| value | number
| The rolled or calculated value of this roll. |
| label | string
| The display label for this roll. This property is optional. |
| order | number
| A property used to maintain ordering of dice rolls within groups. |
RollType
An enum of the valid types of roll. The possible values are:
GroupedRoll
An intermediate interface extended for groups of dice. This interface extends RollBase
.
| Property | Type | Description |
| -------- | ---------------------------------- | ----------------------------------------- |
| dice | Array<
RollBase
>
| The rolls included as part of this group. |
DiceExpressionRoll
A representation of a dice expression. This interface extends GroupedRoll
.
Example
2d20 + 6d6
| Property | Type | Description |
| -------- | -------------------------------------------------------------- | --------------------------------------------- |
| type | "diceexpressionroll"
| The type of roll that this object represents. |
| ops | Array<
DiceGroupMathOperation
>
| The operations to perform on the rolls. |
ExpressionRoll
A representation of a mathematic expression. This interface extends GroupedRoll
.
Example
20 * 17
| Property | Type | Description |
| -------- | -------------------------------------------- | --------------------------------------------- |
| type | "expressionroll"
| The type of roll that this object represents. |
| ops | Array<
MathOperation
>
| The operations to perform on the rolls. |
MathFunctionRoll
A representation of a mathematic function. This interface extends RollBase
.
Example
floor(20 / 17)
| Property | Type | Description |
| -------- | ------------------------------- | ------------------------------------------------- |
| type | "expressionfunc"
| The type of roll that this object represents. |
| op | MathFunction
| The operations to perform on the rolls. |
| expr | RollBase
| The expression that the function is applied upon. |
GroupRoll
A representation of a group of rolls
Example
{4d6,3d6}. This interface extends
GroupedRoll
.
| Property | Type | Description |
| -------- | ------------- | --------------------------------------------- |
| type | "grouproll"
| The type of roll that this object represents. |
DiceRollResult
The rolled result of a group of dice. This interface extends RollBase
.
Example
6d20
| Property | Type | Description |
| -------- | ------------------------------- | --------------------------------------------- |
| die | RollBase
| The die this result represents. |
| type | "die"
| The type of roll that this object represents. |
| rolls | DieRollBase
[] | Each roll of the die. |
| count | RollBase
| The number of rolls of the die. |
| matched | boolean
| Whether this is a match result. |
DieRollBase
An intermediate interface extended for individual die rolls (see below). This interface extends RollBase
.
| Property | Type | Description |
| -------- | --------- | ----------------------------- |
| roll | number
| The rolled result of the die. |
| matched | boolean
| Whether this roll is a match. |
DieRoll
A roll on a regular die. This interface extends DieRollBase
.
Example
d20
| Property | Type | Description |
| -------- | ------------------------------- | -------------------------------------------------------------- |
| die | number
| The die number to be rolled. |
| type | "roll"
| The type of roll that this object represents. |
| critical | CriticalType
| If this role is a critical success or failure (for rendering). |
FateDieRoll
A roll on a fate die. This interface extends DieRollBase
.
Example
dF
| Property | Type | Description |
| -------- | ------------ | --------------------------------------------- |
| type | "fateroll"
| The type of roll that this object represents. |
Parsed Roll Output
The following interfaces are exposed by the library as a reresentation of the parsed input string. The response from the parse
method is a RootType
object and could be any of the interfaces that extend it.
ParsedObjectType
An enum of the valid types of roll. The possible values are:
"number"
"inline"
"success"
"failure"
"crit"
"critfail"
"match"
"keep"
"drop"
"group"
"diceExpression"
"sort"
"explode"
"compound"
"penetrate"
"reroll"
"rerollOnce"
"target"
"die"
"fate"
"expression"
"math"
"mathfunction"
ParsedType
This is the base interface for all parsed types.
| Property | Type | Description |
| -------- | -------- | ----------------------------------------------- |
| type | string
| The type of parsed item this object represents. |
RootType
This is the base interface for a subset of parsed types, only those that can be the root type. This object extends the ParsedType
interface.
| Property | Type | Description |
| -------- | --------- | ----------------------------------------------------------------- |
| label? | string
| The text label attached to this roll. This property is optional. |
| root | boolean
| A boolean flag to indicate if this is the root of the parse tree. |
NumberType
This object represents a single number in the input. This object extends the RootType
interface.
| Property | Type | Description |
| -------- | ---------- | ----------------------------------------------- |
| type | "number"
| The type of parsed item this object represents. |
| value | number
| The value of the number. |
InlineExpression
This object represents an inline dice expression within a string, wrapped in double square brackets. This object extends the RootType
interface.
Example
I want to roll [[2d20]] dice
| Property | Type | Description |
| -------- | --------------------------- | ---------------------------------------------------- |
| type | "inline"
| The type of parsed item this object represents. |
| expr | Expression
| The expression that was parsed as the inline string. |
AnyRoll
A combined type representing any valid roll. This is a combination of the following types:
ModGroupedRoll
This object represents a grouped roll with an optional modifier. This object extends the RootType
interface.
Example
{4d6+3d8}kh1
| Property | Type | Description |
| -------- | ---------------------------------------------------------------------------------------------------- | ------------------------------------------------ |
| mods | Array<
KeepDropModType
,
SuccessFailureModType
>
| The modifiers to be applied to the grouped roll. |
SuccessFailureCritModType
An object representing a success test modifier. This object extends the ParsedType
interface.
A "success"
or "failure"
modifier converts the result into a success type result which returns the number of rolls that meet the target.
A "crit"
or "critfail"
modifier tests the roll for whether or not the roll should be displayed as a critical success or critical failure.
Example
Success:
3d6>3
Failure:3d6f<3
| Property | Type | Description |
| -------- | ------------------------------------------ | ------------------------------------------------- |
| type | "success", "failure", "crit", "critfail"
| The type of parsed item this object represents. |
| mod | CompareOperation
| The check type to use for the condition. |
| expr | RollExpression
| An expression representing the success condition. |
SuccessFailureModType
Equivalent to the SuccessFailureCritModType
but only supporting "success" and "failure" modifiers. This object extends the SuccessFailureCritModType
interface.
Example
Success:
3d6>3
Failure:3d6f<3
| Property | Type | Description |
| -------- | --------------------------------------- | ------------------------------------------------- |
| type | "success", "failure"
| The type of parsed item this object represents. |
| mod | CompareOperation
| The check type to use for the condition. |
| expr | RollExpression
| An expression representing the success condition. |
MatchModType
An object representing a match type modifier, used to modify the display of dice output in roll20. This object extends the ParsedType
interface.
Example
2d6m
When used with the mt
extension, will return the number of matches found.
Example
20d6mt
Additional arguments can be specified that increase the required number of matches or to add a constraint to matches.
Example
20d6mt3 counts matches of 3 items
Example
20d6m>3 Only counts matches where the rolled value is > 3
| Property | Type | Description |
| -------- | --------------------------------------- | ------------------------------------------------------------------------------------------------------ |
| type | "match"
| The type of parsed item this object represents. |
| min | NumberType
| The minimum number of matches to accept. This property defaults to 2 as a NumberType
. |
| count | boolean
| Whether or not to count the matches. |
| mod? | CompareOperation
| The check type to use for the match condition, if specified. This field is optional. |
| expr? | RollExpression
| An expression representing the match condition, if specified. This field is optional. |
KeepDropModType
An object representing a keep or drop modifier, specifying a number of dice rolls to keep or drop, either the highest or lowest rolls. This object extends the ParsedType
interface.
Example
Keep:
2d20kh1
Drop:2d20dl1
| Property | Type | Description |
| -------- | ----------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| type | "keep", "drop"
| The type of parsed item this object represents. |
| highlow | HighLowType
| Whether to keep/drop the highest or lowest roll. |
| expr | RollExpression
| An expression representing the number of rolls to keep/drop. This property defaults to 1 as a NumberType
. Example: 2d6
|
GroupedRoll
This object represents a group of rolls combined, with optional modifiers. This object extends the ModGroupedRoll
interface.
Example
{2d6,3d6}
| Property | Type | Description |
| -------- | ---------------------------------------------- | ----------------------------------------------- |
| type | "group"
| The type of parsed item this object represents. |
| rolls | Array<
RollExpression
>
| The group of rolls included in this group. |
RollExpressionType
An object representing a roll expression including complex rolls and groups, only allows addition operations. This object extends the RootType
interface.
Example
{2d6,3d6}kh1 + {3d6 + 2d6}kh2
| Property | Type | Description |
| -------- | ----------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------- |
| head | RollOrExpression
| The initial roll or expression for the roll expression. |
| type | "diceExpression"
| The type of parsed item this object represents. |
| ops | Array<
MathType
<
RollOrExpression
,
DiceGroupMathOperation
>>
| The operations to apply to the initial roll or expression. |
RollExpression
A helper type combination of a complex roll expression, a roll, or a math expression. Represents the following types:
RollOrExpression
A helper type combination of a roll, or a math expression. Represents the following types:
FullRoll
An object representing a roll including the dice roll, and any modifiers. This object extends the DiceRoll
interface.
Example
2d6kh1
| Property | Type | Description |
| -------- | ---------------------------------------------------------------------------- | ----------------------------------------------------------------------- |
| mods? | Array<
ReRollMod
,
KeepDropModType
>
| Any modifiers attached to the roll. This property is optional. |
| targets? | Array<
SuccessFailureCritModType
>
| Any success or failure targets for the roll. This property is optional. |
| match? | MatchModTyp
| Any match modifiers for the roll. This property is optional. |
| sort? | SortRollType
| Any sort operations to apply to the roll. This property is optional. |
SortRollType
A sort operation to apply to a roll. This object extends the ParsedType
interface.
Example
10d6sa
| Property | Type | Description |
| -------- | --------- | ----------------------------------------------- |
| type | "sort"
| The type of parsed item this object represents. |
| asc | boolean
| Whether to sort ascending or descending. |
ReRollMod
An object representing a re-roll operation to apply to a roll. Can be one of the following types:
"explode"
: re-rolls any dice that meet the target, continuing if the new roll matches"compound"
: re-rolls any dice that meet the target, continuing if the new roll matches and adding the results into a single roll"penetrate"
: re-rolls any dice that meet the target subtracting 1 from the new value, continuing if the new roll matches"reroll"
: re-rolls a die as long as it meets the target, keeping the final roll"rerollOnce"
: re-rolls a die once if it meets the target, keeping the new roll
Example
2d6!
| Property | Type | Description |
| -------- | ------------------------------------------------------------ | ------------------------------------------------------ |
| type | "explode", "compound", "penetrate", "reroll", "rerollOnce"
| The type of parsed item this object represents. |
| target | TargetMod
| The target modifier to compare the roll value against. |
TargetMod
An object represting a target modifier to apply to a roll. This object extends the ParsedType
interface.
| Property | Type | Description |
| -------- | --------------------------------------- | ------------------------------------------------------ |
| type | "target"
| The type of parsed item this object represents. |
| mod | CompareOperation
| The check type to use for the condition. |
| value | RollExpr
| An expression representing the target condition value. |
DiceRoll
The representation of a die roll. This object extends the RootType
interface.
Example
2d6
| Property | Type | Description |
| -------- | ------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| die | RollExpr
,
FateExpr
| The die value to roll against, can be a fate die, a number or a complex roll expression. |
| count | RollExpr
| The number of time to roll this die. |
| type | "die"
| The type of parsed item this object represents. |
FateExpr
The representation of a fate die roll. This object extends the ParsedType
interface.
Example
2dF
| Property | Type | Description |
| -------- | -------- | ----------------------------------------------- |
| type | "fate"
| The type of parsed item this object represents. |
RollExpr
A helper type combination of a number or value that is not an expression. Represents the following types:
Expression
A helper type combination of expression types. Represents the following types:
MathExpression
A math type expression between two or more dice rolls. This object extends the RootType
interface.
Example
2d6 + 3d6 * 4d6
| Property | Type | Description |
| -------- | ----------------------------------------------------------- | ----------------------------------------------- |
| head | AnyRoll
| The initial roll to perform operations against. |
| type | "expression"
| The type of parsed item this object represents. |
| ops | Array<
MathType
<
AnyRoll
>>
| The operations to apply to the initial roll. |
MathType
An object representating an roll math operation to be applied and the value to apply it to. This object extends the ParsedType
interface.
The interface for this object takes a templated type TailType
which specifies the type of the second value used in the operation.
There is a second templated type OpValues
which specifies the type of operations that can be used. This defaults to Array<
MathOperation
>`.
Example
+ 3d6 (as part of 2d6 + 3d6)
| Property | Type | Description |
| -------- | ---------- | ----------------------------------------------- |
| type | "math"
| The type of parsed item this object represents. |
| op | OpValues
| The math operation to perform. |
| tail | TailType
| The second value to use in the operation. |
MathFunctionExpression
An object representing a math function to be applied and the expression to apply it to. This object extends the RootType
interface.
Example
floor(3d6 / 2d4)
| Property | Type | Description |
| -------- | ------------------------------- | ----------------------------------------------- |
| type | "mathfunction"
| The type of parsed item this object represents. |
| op | MathFunction
| The function to be applied. |
| expr | AnyRoll
| The expression to apply the function on. |
Helper Types
The following are support types used by the above interfaces.
DiceGroupMathOperation
A helper type representing the valid operations for a math operation on a group of dice.
"+" | "-"
MathOperation
A helper type representing the valid operations for a math operation.
"+" | "-" | "*" | "/" | "%" | "**"
MathFunction
A helper type representing the valid operations for a math operation.
"floor" | "ceil" | "round" | "abs"
CriticalType
A helper type used when marking a roll as a critical success or failure.
"success" | "failure" | null
CompareOperation
A helper type for the available operations for a comparison point.
">" | "<" | "="
HighLowType
A helper type used to determine which rolls to keep or drop.
"h" | "l" | null