code: function makeUrl(s) {
    var search = window.location.search;
  
    // Remove previous grep query parameter if present
    if (search) {
      search = search.replace(/[?&]grep=[^&\s]*/g, '').replace(/^&/, '?');
    }
  
    return (
      window.location.pathname +
      (search ? search + '&' : '?') +
      'grep=' +
      encodeURIComponent(escapeRe(s))
    );
  }
docs: Makes a URL, preserving querystring ("search") parameters.
  
  @param {string} s
  @return {string} A new URL.