@formatjs/intl-pluralrules/abstract/ResolvePluralRange.js

Polyfill for Intl.PluralRules

import { invariant, Type } from "@formatjs/ecma402-abstract";
import "./GetOperands.js";
import { ResolvePluralInternal } from "./ResolvePlural.js";
/**
* ResolvePluralRange ( pluralRules, x, y )
*
* The ResolvePluralRange abstract operation is called with arguments pluralRules (which must be
* an object initialized as a PluralRules), x (a mathematical value), and y (a mathematical value).
* It resolves the appropriate plural form for a range by determining the plural forms of both the
* start and end values, then consulting locale-specific range data.
*
* Specification: https://tc39.es/ecma402/#sec-resolvepluralrange
*
* @param pluralRules - An initialized PluralRules object
* @param x - Mathematical value for the range start
* @param y - Mathematical value for the range end
* @returns The plural category for the range (zero, one, two, few, many, or other)
*/
export function ResolvePluralRange(pluralRules, x, y, { getInternalSlots, PluralRuleSelect, PluralRuleSelectRange }) {
	// 1. If x is not-a-number or y is not-a-number, throw a RangeError exception.
	if (!x.isFinite() || !y.isFinite()) {
		throw new RangeError("selectRange requires start and end values to be finite numbers");
	}
	// Validation: Assert that pluralRules has been initialized
	const internalSlots = getInternalSlots(pluralRules);
	invariant(Type(internalSlots) === "Object", "pluralRules has to be an object");
	invariant("initializedPluralRules" in internalSlots, "pluralrules must be initialized");
	// 2. Let xp be ResolvePlural(pluralRules, x).
	// Note: ResolvePlural returns a Record with [[FormattedString]] and [[PluralCategory]]
	const xp = ResolvePluralInternal(pluralRules, x, {
		getInternalSlots,
		PluralRuleSelect
	});
	// 3. Let yp be ResolvePlural(pluralRules, y).
	const yp = ResolvePluralInternal(pluralRules, y, {
		getInternalSlots,
		PluralRuleSelect
	});
	// 4. If xp.[[FormattedString]] is yp.[[FormattedString]], then
	//    a. Return xp.[[PluralCategory]].
	// Note: When the formatted strings are identical (e.g., "1" and "1"), the values are
	// effectively the same, so we return the plural category of the start value.
	if (xp.formattedString === yp.formattedString) {
		return xp.pluralCategory;
	}
	// 5. Let locale be pluralRules.[[Locale]].
	// 6. Let type be pluralRules.[[Type]].
	const { locale, type } = internalSlots;
	// 7. Let notation be pluralRules.[[Notation]].
	// 8. Let compactDisplay be pluralRules.[[CompactDisplay]].
	// Note: notation and compactDisplay are not yet implemented for PluralRules polyfill.
	// When implemented, these would affect how the range is formatted and thus which
	// plural rules apply (see c/e operand support).
	// 9. Return PluralRuleSelectRange(locale, type, notation, compactDisplay, xp.[[PluralCategory]], yp.[[PluralCategory]]).
	// Note: PluralRuleSelectRange is implementation-defined and uses CLDR plural range data
	// to determine the appropriate plural category for a range based on the start and end categories.
	// Example: In English, "one" to "other" → "other" (e.g., "1-2 items")
	return PluralRuleSelectRange(locale, type, xp.pluralCategory, yp.pluralCategory);
}