Handlebars helper for pluralizing most words

//dependencies: jQuery and string.js (http://stringjs.com/)
//usage: {{pluralize num 'word'}}

Handlebars.registerHelper('pluralize', function(number, str) {
    //doesn't handle weird words
    var lastLetter = str[str.length - 1]
        , strObj = S(str)
        , vowels = ['a', 'e','i','o','u']
        , root = str
        , suffix = 's'
    ;
    if (+number !== 1) {
        //possible weird cases
        if (strObj.endsWith('man')) {
            return strObj.chompRight('man').s + 'men';
        }
        if (str === 'person') {
            return 'people';
        }
        //rule-based cases
        switch (lastLetter) {
            case 'o':
            case 'x':
            case 'z': //intentional fallthrough
                suffix = 'es';
                break;
            case 'e':
                if (strObj.endsWith('fe')) {
                    root = strObj.chompRight('fe').s;
                    suffix = 'ves';
                }
                break;
            case 'f':
                if (strObj.endsWith('arf') || strObj.endsWith('lf') || strObj.endsWith('af')) {
                    root = strObj.chompRight('f').s;
                    suffix = 'ves';
                }
                break;
            case 'h':
                if (strObj.endsWith('sh') || strObj.endsWith('ch')) {
                    suffix = 'es';
                }
                break;
            case 's':
                if (!strObj.endsWith('ies')) {
                    suffix = 'es';
                }
                break;
            case 'y':
                //ends in [consonant]y
                if ($.inArray(str[str.length - 2], vowels) === -1 || strObj.endsWith('quy')) {
                    root = strObj.chompRight('y').s;
                    suffix = 'ies';
                }
                break;
        }
        return root + suffix;
    }
    return str;
});