jQuery plugin to get sum of selected input values

jquery-sum.js

(function ($) {
    /**
     * jQuery plugin to get sum of selected input values
     * Usage syntax:
     * $('selector').sum()
     * $('selector').sum(initial_value)
     * $('selector').sum(parse_type)
     * $('selector').sum(parse_type, initial_value)
     */
    $.fn.sum = function (parse_type, initial_value) {
        var parseType = typeof parse_type === 'function' ? parse_type : parseFloat;
        var initialValue = parseType(typeof parse_type !== 'function' ? parse_type : initial_value) || 0;
        var mapper = function () {
            return parseType($(this).val() || 0);
        };
        var reducer = function (accumulator, currentValue) {
            return accumulator + currentValue;
        };
        return initialValue + this.map(mapper).get().reduce(reducer);
    };
})(jQuery);