Class PTable<T>

A probability table is a set of items that have an assigned probability.

The goal of the probability table is to make it quick and easy to assign a set chance on multiple outcomes of a single event.

import {PTable} from "ptable";
const p = new PTable<string>();
p.add({value: "blah", weight: 1}); // add an entry for the string "blah" with a weight of 1
p.create("cake", 2); // shortcut for adding a string "cake" with a weight of 2
p.create("pie", 5);

for(let i=0;i<10000;i++){
	const result = p.roll();
}
// ...

Type Parameters

  • T

Constructors

constructor

Properties

editMode entries totalWeight

Methods

add create initializeEntryRanges populate preroll roll

Constructors

constructor

Properties

ProtectededitMode

editMode: boolean = false

entries

entries: PTableEntry<T>[] = []

ProtectedtotalWeight

totalWeight: number = 0

Methods

add

  • add(...entries): void

  • Add a series of entries to the PTable.

    After adding all entries, the probability ranges will be re-intialized for all entries based on the change in the total weight of all entries added.

    When adding lots of entries, you may want to look into PTable#populate.

    Parameters

    • Rest...entries: PrePTableEntry<T>[]

      The set of precursor PTable entries to add.

    Returns void

    See

    PTable#populate

create

  • create(value, weight): void

  • Create a new PTable entry.

    Parameters

    • value: T

      The value of the entry.

    • weight: number

      The weight of the entry.

    Returns void

ProtectedinitializeEntryRanges

  • initializeEntryRanges(): void

  • Re-calculates the ranges of all entries based on their weights.

    Called every time a new entry is added, unless edit mode is enabled.

    Returns void

    See

    PTable#populate

populate

  • populate(edit): void

  • Enables edit mode, which disables re-initializing entry ranges with every addition.

    Edit mode is only enabled during the call of the provided callback function, which is executed immediately.

    After the callback function ends, edit mode is disabled.

    Parameters

    • edit: (() => void)

      A function called during edit mode.

        • (): void

        • Returns void

    Returns void

preroll

  • preroll(p): T

  • Accepts a P value between 0 and 1 that corresponds to the range of an entry in the PTable.

    If the p value falls within the range of the entry, its value will be returned.

    Parameters

    • p: number

      A value between 0 and 1.

    Returns T

    The value of the chosen entry.

    Throws

    Attempting to roll an empty PTable.

    Throws

    Failed to return a result. This generally means the provided P value is not within the range of any entries.

roll

  • roll(): T

  • Generate a random number to use to pick an entry from the table.

    Returns T

    The rolled entry's value.

    Throws

    Attempting to roll an empty PTable.

    Throws

    Failed to return a result. This generally means the provided P value is not within the range of any entries.

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