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A Fischer Random Chess / Chess960 JavaScript library based on algorithms.

letsp=fischer.random()sp.id// -> 518sp.arrangement// -> ['R', 'N', 'B', 'Q', 'K', 'B', 'N', 'R']

npm:npm i fischer960
yarn:yarn add fischer960
pnpm:pnpm add fischer960

There are no dependencies.

One can import only the functions to be used:

import{random,toString,toUnicode}from'fischer960'

But importing the whole library will let you writefischer.random() 😎

import*asfischerfrom'fischer960'letsp=fischer.random()

A few things to be aware of:

• IDs are zero-indexed (0-959, the standard starting position being 518)
• random() anddecode() return the arrangement as an array (to convert the array to a string, seetoString())
• Allarrangement arguments can take either an array (['B', 'B', 'Q', 'N', 'N', 'R', 'K', 'R']) or a string ('BBQNNRKR')

Generates a random starting position, returning its ID and arrangement of pieces.

random()// -> eg. { id: 518, arrangement: ['R', 'N', 'B', 'Q', 'K', 'B', 'N', 'R'] }

Picks a random starting position's ID.

randomID()// -> eg. 518

Given an ID, returns the starting position's arrangement of pieces, orfalse if the ID is invalid.

decode(518)// -> eg. ['R', 'N', 'B', 'Q', 'K', 'B', 'N', 'R']

Given an arrangement of pieces, returns the starting position's ID, or-1 if the arrangement is invalid.

encode('RKRNNQBB')// -> 959

A set of helper functions for manipulating arrangements are also provided.

Except fortoString() andtoArray(), these functions return the same type as was provided (if you pass a string you get a string, if you pass an array you get an array). Except fortoLowerCase() andtoUpperCase(), these also return the same case as was provided.

Converts an arrangement of pieces fromArray toString.

toString(['B','B','Q','N','N','R','K','R'])// -> 'BBQNNRKR'

Converts an arrangement of pieces fromString toArray.

toArray('BBQNNRKR')// -> ['B', 'B', 'Q', 'N', 'N', 'R', 'K', 'R']

Converts an arrangement of pieces to lowercase notation.

toLowerCase('BBQNNRKR')// -> 'bbqnnrkr'

Converts an arrangement of pieces to uppercase notation.

toUpperCase('bbqnnrkr')// -> 'BBQNNRKR'

Mirrors an arrangement of pieces (returns its “twin”).

toMirror('BBQNNRKR')// -> 'RKRNNQBB'

Converts an arrangement of pieces to Unicode symbols.

Thecolor argument is optional and defaults to white (falsy = white, truthy = black).

Note: There's no way to convert back to letters from Unicode symbols.

toUnicode('BBQNNRKR')// -> '♗♗♕♘♘♖♔♖'toUnicode('BBQNNRKR',true)// -> '♝♝♛♞♞♜♚♜'

Validates a starting position's arrangement of pieces.

isValidArrangement('BBQNNRKR')// -> trueisValidArrangement('KQRBRBNN')// -> false (not a valid starting position)

Validates a starting position's ID.

Note:960 is not a valid ID, as this library uses zero-based IDs.

isValidID(0)// -> trueisValidID(960)// -> false