I'm looking for a modern Ajax script which detects if Ajax exists. One that has been tested to be quick and reliable.

I don't need it to do anything, only for it to send data to the server and receive the server's response.

I prefer for it not to be with jQuery or any other library.

I know the immediate response will be to tell me to check Google, and I have done, but I want one that is recommended by someone in the know and it must have a brilliant, reliable detection script that detects for Ajax support. I expect my websites to work on mobile devices and if full Ajax support isn't available then I want to offer fallback.

Something like this would be ideal:

executeAjax(variables) {

 if(Ajax) {
  url = "file.php?" + variables;
  //perform action

  return server_response_text;   
 } else {

  return false;