String

`String.prototype.localeCompare`

Returns a number indicating whether the reference string comes before, after, or is equivalent to the given string in sort order

Syntax

JavaScript

string.localeCompare(compareString, locales?, options?)

Parameters

Parameter	Type	Description
compareString	string	The string to compare against
locales	string \| string[]	A BCP 47 language tag or array of tags
options	Intl.CollatorOptions	Options for the comparison

Return Value

Negative if before, positive if after, 0 if equivalent

Examples

Basic Usage

console.log('a'.localeCompare('b')); // -1
console.log('b'.localeCompare('a')); // 1

Practical Example

const items = ['résumé', 'cafe', 'naïve', 'über'];
items.sort((a, b) => a.localeCompare(b));
console.log(items);

Advanced Usage

const a = 'ä';
console.log(a.localeCompare('z', 'de')); // negative (ä sorts before z in German)

Understanding String.prototype.localeCompare

The String.prototype.localeCompare method in JavaScript returns a number indicating whether the reference string comes before, after, or is equivalent to the given string in sort order. It belongs to the String object and is one of the most widely used methods for working with string values in modern JavaScript and TypeScript applications.

The method signature is string.localeCompare(compareString, locales?, options?). It accepts 3 parameters: compareString, locales, options. When called, it returns negative if before, positive if after, 0 if equivalent. Understanding when and how to use localeCompare() helps you write more expressive, readable code.

Common use cases for String.prototype.localeCompare include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like string-normalize, array-sort, string-tolowercase, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for String.prototype.localeCompare is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.