/**
 * get url parameter by name
 * @param name parameter name
 * @param url url target, null for current location.href
 * @see https://stackoverflow.com/a/901144
 * @returns
 * @example
 * ```js
 * // 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)
 * ```
 */
function getParameterByName(name: string, url: string | null = null) {
    if (typeof URLSearchParams !== "undefined") {
        if (!window.location.search) {
            url = window.location.href;
        } else {
            url = window.location.search;
        }
        const urlParams = new URLSearchParams(url);
        return urlParams.get(name);
    }
    if (!url) {
        url = window.location.href;
    }
    name = name.replace(/[\[\]]/g, "\\$&");
    const regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
        results = regex.exec(url);
    if (!results) return null;
    if (!results[2]) return "";
    return decodeURIComponent(results[2].replace(/\+/g, " "));
}