LexoRank

A lightweight immutable class implementation of the LexoRank ranking system by Atlassian JIRA.

Features

This library provides the following functionality with unbounded rank lengths:

• Creating ranks
• Incrementing & decrementing ranks
• Finding a rank between two other ranks

Usage

Create and read rank.

const rank = new LexoRank('zc4b', '0');
// or
// const rank = new LexoRank('zc4b'); // default bucket of `0`
// or
// const rank = LexoRank.from('0|zc4b');

expect(rank.toString()).toBe('0|zc4b');
expect(rank.bucket).toBe('0');
expect(rank.value).toBe('zc4b');

Ranks ending in 0 are disallowed to avoid ajacencies. As a result, there is always room to insert between two unequal ranks.

expect(new LexoRank('2c0', '1')).toThrow('Invalid lex value');
expect(LexoRank.from('1|2c0')).toThrow('Invalid lex string');

Increment a rank.

const rank = new LexoRank('a3c', '2');
const newRank = rank.increment();

expect(rank.toString()).toBe('2|a3c');
expect(newRank.toString()).toBe('2|a3d');

const rank = new LexoRank('x2z');
const newRank = rank.increment();

expect(rank.toString()).toBe('0|x2z');
expect(newRank.toString()).toBe('0|x3');

Decrement a rank.

const rank = new LexoRank('a3c', '2');
const newRank = rank.decrement();

expect(rank.toString()).toBe('2|a3c');
expect(newRank.toString()).toBe('2|a3b');

const rank = new LexoRank('z1');
const newRank = rank.decrement();

expect(rank.toString()).toBe('0|z1');
expect(newRank.toString()).toBe('0|z');

const rank = new LexoRank('03001');
const newRank = rank.decrement();

expect(rank.toString()).toBe('0|03001');
expect(newRank.toString()).toBe('0|03');

const rank = new LexoRank('01');
const newRank = rank.decrement();

expect(rank.toString()).toBe('0|01');
expect(newRank.toString()).toBe('0|001');

Get a rank in between two ranks

const rank1 = new LexoRank('9a2r');
const rank2 = new LexoRank('9a3r');

const btwn = LexoRank.between(rank1, rank2);
expect(btwn.toString()).toBe('0|9a2s');

const btwn = LexoRank.between('0|e5z', '0|e6');
expect(btwn.toString()).toBe('0|e5z1');

const btwn = LexoRank.between('0|e5z1', '0|e5z11');
expect(btwn.toString()).toBe('0|e5z101');

const btwn = LexoRank.between('0|e5z1', null);
expect(btwn.toString()).toBe('0|e5z2');

const btwn = LexoRank.between(null, '0|e5z11');
expect(btwn.toString()).toBe('0|e5z1');