getPluralForm.js

/**
 * Chooses plural form of a word that corresponds to a number
 *
 * @param {number} number The number
 * @param {string} zeroCaseForm Zero-ending form (ворон)
 * @param {string} oneCaseForm One-ending form (ворона)
 * @param {string} twoCaseForm Two-ending form (вороны)
 *
 * @returns {string} Plural form of the word
 */
function getPluralForm(number, zeroCaseForm, oneCaseForm, twoCaseForm) {
    var lastDigit = String(number).slice(-1);

    switch (lastDigit) {
        case '0':
        case '9':
        case '8':
        case '7':
        case '6':
        case '5':
            return zeroCaseForm;

        case '4':
        case '3':
        case '2':
            return twoCaseForm;

        case '1':
            return oneCaseForm;

        default:
            return;
    }
}