Set Order

Tiny module for sorting by a set order, using a custom sort function for omitting explicits.

npm i set-order --save

Useful for when you have an array of dynamic data, but you need to sort by a set order, rather than a natural sort order, such as alphabetically or numerically.

Getting Started

Picture a scenario where you have a set of bedroom counts where if the count is zero then it's labelled as Studio. Using the typical sort function would yield the following unusual result.

const bedrooms = [4, 2, 'Studio', 1, 3];

bedrooms.sort((a, b) => a > b);

Result: [2, 4, 'Studio', 1, 3]

However by utilising set-order you can be explicit in specifying that Studio must always be at the beginning.

import { exact } from 'set-order';

const bedrooms = [4, 2, 'Studio', 1, 3];
bedrooms.sort(exact(['Studio', 1, 2, 3, 4]));

💎 Result: ['Studio', 1, 2, 3, 4]

However the problem with the above is obvious — you need to be explicit in specifying all of the possible bedroom counts, which could be into their hundreds for a chateau. Using the third parameter of the exact function allows you to specify a typical sort comparator ((a, b) => a > b) for unspecified items.

import { exact } from 'set-order';

const bedrooms = [4, 2, 'Studio', 1, 3];
bedrooms.sort(exact(['Studio'], (a, b) => a - b));

💎 Result: ['Studio', 1, 2, 3, 4]

Assume now that we've added an additional item named etc... that must appear at the end – to achieve that we use the position key which defaults to head.

import { exact, tail } from 'set-order';

const bedrooms = [4, 'etc...', 2, 'Studio', 1, 3];
bedrooms.sort(exact([
    { value: 'Studio' },
    { value: 'etc...', position: tail }
], (a, b) => a - b));

💎 Result: ['Studio', 1, 2, 3, 4, 'etc...']

Nevertheless in real-life scenarios the bedroom counts will likely be an item in an object, that is then contained within an array which we can target by using property.

import { exact, tail } from 'set-order';
import by              from 'sort-by';

const bedrooms = [
    { id: 1, bedrooms: 4 },
    { id: 2, bedrooms: 'etc...' },
    { id: 3, bedrooms: 2 },
    { id: 4, bedrooms: 'Studio' },
    { id: 5, bedrooms: 1 },
    { id: 6, bedrooms: 3 }
];

bedrooms.sort(exact([
    { property: 'bedrooms', value: 'Studio' },
    { property: 'bedrooms', value: 'etc...', position: tail }
], by('bedrooms')));

💎 Result: [{ id: 4, bedrooms: 'Studio' }, { id: 5, bedrooms: 1' }] etc...