code: function b64tob64u(s) {
      s = s.replace(/\=/g, "");
      s = s.replace(/\+/g, "-");
      s = s.replace(/\//g, "_");
      return s;
  }
docs: ==== base64 / base64url ================================ 
  convert a Base64 encoded string to a Base64URL encoded string.<br/>
  Example: "ab+c3f/==" &rarr; "ab-c3f_"
  @param {String} s Base64 encoded string
  @return {String} Base64URL encoded string