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# String Natural Compare
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[](https://www.npmjs.com/package/string-natural-compare)
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[](https://travis-ci.org/nwoltman/string-natural-compare)
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[](https://coveralls.io/r/nwoltman/string-natural-compare?branch=master)
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[](https://david-dm.org/nwoltman/string-natural-compare)
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Compare alphanumeric strings the same way a human would, using a natural order algorithm (originally known as the [alphanum algorithm](http://davekoelle.com/alphanum.html)) where numeric characters are sorted based on their numeric values rather than their ASCII values.
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```
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Standard sorting: Natural order sorting:
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img1.png img1.png
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img10.png img2.png
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img12.png img10.png
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img2.png img12.png
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```
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This module exports a function that returns a number indicating whether one string should come before, after, or is the same as another string.
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It can be used directly with the native [`.sort()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort) array method.
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### Fast and Robust
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This module can compare strings containing any size of number and is heavily tested with a custom [benchmark suite](https://github.com/nwoltman/string-natural-compare/tree/master/benchmark) to make sure that it is as fast as possible.
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## Installation
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```sh
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npm install string-natural-compare --save
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# or
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yarn add string-natural-compare
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```
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## Usage
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#### `naturalCompare(strA, strB[, options])`
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+ `strA` (_string_)
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+ `strB` (_string_)
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+ `options` (_object_) - Optional options object with the following options:
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+ `caseInsensitive` (_boolean_) - Set to `true` to compare strings case-insensitively. Default: `false`.
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+ `alphabet` (_string_) - A string of characters that define a custom character ordering. Default: `undefined`.
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```js
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const naturalCompare = require('string-natural-compare');
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// Simple, case-sensitive sorting
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const files = ['z1.doc', 'z10.doc', 'z17.doc', 'z2.doc', 'z23.doc', 'z3.doc'];
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files.sort(naturalCompare);
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// -> ['z1.doc', 'z2.doc', 'z3.doc', 'z10.doc', 'z17.doc', 'z23.doc']
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// Case-insensitive sorting
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const chars = ['B', 'C', 'a', 'd'];
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const naturalCompareCI = (a, b) => naturalCompare(a, b, {caseInsensitive: true});
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chars.sort(naturalCompareCI);
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// -> ['a', 'B', 'C', 'd']
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// Note:
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['a', 'A'].sort(naturalCompareCI); // -> ['a', 'A']
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['A', 'a'].sort(naturalCompareCI); // -> ['A', 'a']
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// Compare strings containing large numbers
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naturalCompare(
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'1165874568735487968325787328996865',
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'265812277985321589735871687040841'
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);
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// -> 1
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// (Other inputs with the same ordering as this example may yield a different number > 0)
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// Sorting an array of objects
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const hotelRooms = [
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{street: '350 5th Ave', room: 'A-1021'},
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{street: '350 5th Ave', room: 'A-21046-b'}
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];
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// Sort by street (case-insensitive), then by room (case-sensitive)
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hotelRooms.sort((a, b) => (
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naturalCompare(a.street, b.street, {caseInsensitive: true}) ||
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naturalCompare(a.room, b.room)
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));
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// When text transformation is needed or when doing a case-insensitive sort on a
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// large array of objects, it is best for performance to pre-compute the
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// transformed text and store it on the object. This way, the text will not need
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// to be transformed for every comparison while sorting.
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const cars = [
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{make: 'Audi', model: 'R8'},
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{make: 'Porsche', model: '911 Turbo S'}
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];
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// Sort by make, then by model (both case-insensitive)
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for (const car of cars) {
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car.sortKey = (car.make + ' ' + car.model).toLowerCase();
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}
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cars.sort((a, b) => naturalCompare(a.sortKey, b.sortKey));
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// Using a custom alphabet (Russian alphabet)
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const russianOpts = {
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alphabet: 'АБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯабвгдеёжзийклмнопрстуфхцчшщъыьэюя',
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};
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['Ё', 'А', 'б', 'Б'].sort((a, b) => naturalCompare(a, b, russianOpts));
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// -> ['А', 'Б', 'Ё', 'б']
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```
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**Note:** Putting numbers in the custom alphabet can cause undefined behaviour.
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