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.

1const rank = new LexoRank('zc4b', '0');
2// or
3// const rank = new LexoRank('zc4b'); // default bucket of `0`
4// or
5// const rank = LexoRank.from('0|zc4b');
6
7expect(rank.toString()).toBe('0|zc4b');
8expect(rank.bucket).toBe('0');
9expect(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.

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

Increment a rank.

1const rank = new LexoRank('a3c', '2');
2const newRank = rank.increment();
3
4expect(rank.toString()).toBe('2|a3c');
5expect(newRank.toString()).toBe('2|a3d');

1const rank = new LexoRank('x2z');
2const newRank = rank.increment();
3
4expect(rank.toString()).toBe('0|x2z');
5expect(newRank.toString()).toBe('0|x3');

Decrement a rank.

1const rank = new LexoRank('a3c', '2');
2const newRank = rank.decrement();
3
4expect(rank.toString()).toBe('2|a3c');
5expect(newRank.toString()).toBe('2|a3b');

1const rank = new LexoRank('z1');
2const newRank = rank.decrement();
3
4expect(rank.toString()).toBe('0|z1');
5expect(newRank.toString()).toBe('0|z');

1const rank = new LexoRank('03001');
2const newRank = rank.decrement();
3
4expect(rank.toString()).toBe('0|03001');
5expect(newRank.toString()).toBe('0|03');

1const rank = new LexoRank('01');
2const newRank = rank.decrement();
3
4expect(rank.toString()).toBe('0|01');
5expect(newRank.toString()).toBe('0|001');

Get a rank in between two ranks

1const rank1 = new LexoRank('9a2r');
2const rank2 = new LexoRank('9a3r');
3
4const btwn = LexoRank.between(rank1, rank2);
5expect(btwn.toString()).toBe('0|9a2s');

1const btwn = LexoRank.between('0|e5z', '0|e6');
2expect(btwn.toString()).toBe('0|e5z1');

1const btwn = LexoRank.between('0|e5z1', '0|e5z11');
2expect(btwn.toString()).toBe('0|e5z101');

1const btwn = LexoRank.between('0|e5z1', null);
2expect(btwn.toString()).toBe('0|e5z2');

1const btwn = LexoRank.between(null, '0|e5z11');
2expect(btwn.toString()).toBe('0|e5z1');