some utility to help building urls

url-tools.ts

export function base_href() {
  try {
    const base = document
      .getElementsByTagName('base')
      .item(0)
      .getAttribute('href');
    return base !== '/' ? base : null;
  } catch (e) {
    return null;
  }
}
export function local_url(pathElements): string {
  const loc = window.location;
  let args = Array.isArray(pathElements) ? pathElements : [pathElements];
  args = [base_href(), ...args];
  const path = args.filter(i => (i || '').length > 0).join('/');
  return `${loc.protocol}://${loc.host}/${path}`;
}