### URLJoin Joins all given URL segments together, then normalizes the resulting URL. Use `String.join('/')` to combine URL segments, then a series of `String.replace()` calls with various regexps to normalize the resulting URL (remove double slashes, add proper slashes for protocol, remove slashes before parameters, combine parameters with `'&'` and normalize first parameter delimiter). ```js const URLJoin = (...args) => args .join('/') .replace(/[\/]+/g, '/') .replace(/^(.+):\//, '$1://') .replace(/^file:/, 'file:/') .replace(/\/(\?|&|#[^!])/g, '$1') .replace(/\?/g, '&') .replace('&', '?'); ``` ```js URLJoin('http://www.google.com', 'a', '/b/cd', '?foo=123', '?bar=foo'); // 'http://www.google.com/a/b/cd?foo=123&bar=foo' ```