README.md

unicode-case-folding

A JavaScript library for Unicode case folding based on the official Unicode Character Database.

What is Case Folding?

Case folding is the process of removing case distinctions in a string. It's similar to case conversion but specifically designed for case-insensitive comparisons rather than display.

Unlike simple case conversion, Unicode case folding follows specific rules defined in the Unicode standard to ensure proper internationalized case-insensitive comparisons.

Installation

npm install unicode-case-folding

Usage

import { caseFold, caseFoldEquals } from "unicode-case-folding";

// Basic case folding
const folded = caseFold("Hello World");
console.log(folded); // "hello world"

// Case-insensitive comparison
console.log(caseFoldEquals("HELLO", "hello")); // true
console.log(caseFoldEquals("ẞ", "ss")); // true (German sharp S)
console.log(caseFoldEquals("Straße", "strasse")); // true

// Special case foldings
console.log(caseFold("ẞ")); // "ss" (German sharp S folds to "ss")

API

caseFold(string)

Applies Unicode case folding to the input string.

• Parameters: string - The string to case fold
• Returns: The case-folded string

caseFoldEquals(string1, string2)

Compares two strings for equality using Unicode case folding.

• Parameters:
  • string1 - First string to compare
  • string2 - Second string to compare
• Returns: true if the strings are case-fold equivalent, false otherwise

lookupFolding(codePoint)

Returns the case folding mapping for a specific code point.

• Parameters: codePoint - Unicode code point as a number
• Returns: Array of code points this character folds to, or undefined if no folding exists

License

MIT