Better cmp

Usage

const { cmp } = require('better-cmp');
console.assert(cmp([1, 'b', null], [1, 'a']) === 1);
console.assert(cmp([1, {reverse: 'b'}, null], [1, {reverse: 'a'}]) === -1);

Sorting convenience functions

This library provides convenience functions for sorting arrays by key function.

Usage: sortBy(arrayToSort, keyFunction). keyFunction converts array item to sorting criteria.

Example:

const { sortBy } = require('better-cmp/lib/extra');
const dataset = [
    {group: 1, name: 'Foo', value: 3},
    {group: 2, name: 'Bar', value: 1},
    {group: 1, name: 'Baz', value: 2},
];
const sorted = sortBy(dataset, (item) => [item.group, item.value]);
console.assert(sorted.map((item) => item.name).join(',') === 'Baz,Foo,Bar');

Rationale

• Very often, when sorting arrays in JavaScript, you need a comparison function.

• JavaScript has a loosely typed comparison (<, >) and equality (==). It is useful to have a stricter version of comparison.

• It's useful to have a lexicographical comparison of two arrays, if multiple sorting criteria are used.

Specification

• null is smaller than anything else.

• Values of different types throw TypeError, with sole exception of null.

• NaN is smaller than any other number.

• Non-NaN numbers, strings, booleans and BigInts compare as usual.

• Arrays are compared lexicographically, comparing the elements recursively.

• If both values are objects that have a reverse key, they are sorted in reverse order, using the value by that key.

Example:

console.assert(cmp({reverse: 0}, {reverse: 1}) === 1);
console.assert(cmp({reverse: [1, 1]}, {reverse: [1, 2]}) === 1);

• If both values are objects that have a localeCompare key, they are compared using Intl.Collator.
  You can specify a custom collator using collator key.

Example:

// default comparison
console.assert(cmp({localeCompare: 'a'}, {localeCompare: 'A'}) === -1);

// case-insensitive, accent-insensitive comparison
const baseCollator = new Intl.Collator('en', { sensitivity: 'base' });
console.assert(cmp(
    {localeCompare: 'réservé', collator: baseCollator},
    {localeCompare: 'RESERVE', collator: baseCollator}
) === 0);

// case-insensitive, accent-sensitive comparison
const accentCollator = new Intl.Collator('en', { sensitivity: 'accent' });
console.assert(cmp(
    {localeCompare: 'réservé', collator: accentCollator},
    {localeCompare: 'RESERVE', collator: accentCollator}
) === 1);

• Anything else throws TypeError.

There are a few arbitrary decisions made here. NaN could've been placed under zero, but that would produce weird results. The other consistent solution would be to throw on NaN. null is treated as None value, and the type of other variable is ignored.

Tests

Tests are located in src/index.test.ts.

License

MIT

Author

Igor null [e-mail]