@maplibre/maplibre-gl-style-spec/src/expression/types/collator.ts

a specification for maplibre styles

export class Collator {
    locale: string | null;
    sensitivity: 'base' | 'accent' | 'case' | 'variant';
    collator: Intl.Collator;

    constructor(caseSensitive: boolean, diacriticSensitive: boolean, locale: string | null) {
        if (caseSensitive) this.sensitivity = diacriticSensitive ? 'variant' : 'case';
        else this.sensitivity = diacriticSensitive ? 'accent' : 'base';

        this.locale = locale;
        this.collator = new Intl.Collator(this.locale ? this.locale : [], {
            sensitivity: this.sensitivity,
            usage: 'search'
        });
    }

    compare(lhs: string, rhs: string): number {
        return this.collator.compare(lhs, rhs);
    }

    resolvedLocale(): string {
        // We create a Collator without "usage: search" because we don't want
        // the search options encoded in our result (e.g. "en-u-co-search")
        return new Intl.Collator(this.locale ? this.locale : []).resolvedOptions().locale;
    }
}