javascript querystring 파라미터 값

function getParameterByName(name, url) {
    if (!url) {
        url = location.href;
    }
    name = name.replace(/\[\\\[\\\]\]/g, "\\\\$&");
    var regex = new RegExp("\[?&\]" + name + "(=(\[^&#\]\*)|&|#|$)"),
        results = regex.exec(url);
    if (!results) return null;
    if (!results[2]) return '';
    return decodeURIComponent(results[2].replace(/\\+/g, " "));
}

// query string: ?foo=lorem&bar=&baz
var foo = getParameterByName('foo'); // "lorem"
var bar = getParameterByName('bar'); // "" (present with empty value)
var baz = getParameterByName('baz'); // "" (present with no value)
var qux = getParameterByName('qux'); // null (absent)