Send return entire HTML page

responseText is an XHR that says "What the server will respond to the request with, excluding the HTTP headers."

It's perfectly okay for him to include a complete HTML document if you're accessing a resource dedicated to responding to regular form submissions.

It sounds like you need to be smarter about what the server is responding to.

This simple example (written in Perl, see link for more context) checks a query string parameter to decide whether to place the data received in an HTML template and return it, or convert the data to JSON and return it instead.

  if ($view eq "json") {
    my $data = $json->convert_blessed->encode($vars);
    print $q->header('application/json;charset=utf-8'), $data;
    return;
  }

  my $output;
  $tt->process('html.tt', $vars, \$output)
    || die $tt->error(), "\n";

  print $q->header('text/html;charset=utf-8'), $output;