javascriptでのDateオブジェクト作成時のバリデート

gistfile1.js

function isValidDate(date_str) {
    var date = new Date(date_str),
    date_reg = /^(\d{4}|\d{2})(?:\x2d|\u002f)(\d{2}|\d)(?:\x2d|\u002f)(\d{2}|\d)/,

    valid = function() {
        var date_strs = date_str.match(date_reg),
        addDateStr = {};

        addDateStr.date = function() {
            return (date.getFullYear() - 0) + (date.getMonth() - 0) + (date.getDate() - 0);
        };

        addDateStr.str = function() {
            return (date_strs[1] - 0) + (date_strs[2] - 1) + (date_strs[3] - 0);
        };

        if (isNaN(date.getTime()) || !date_strs) return false;

        return addDateStr.date() === addDateStr.str();
    };

    if (Object.prototype.toString.call(date) !== "[object Date]") return false;

    return valid();
}