The production server is behind a firewall as end user can access this from external url.

All other lower environments are not throwing this error, but the production is throwing the error whe we run the script file (below) Server error - $(HttpStatus)

The portion which is causing the error is:

var req = new XMLHttpRequest();

req.open('GET', document.location, false);

req.send(null);

var myHeaders = new Headers();

// associate array to store all values

var data = new Object();

// get all headers in one call and parse each item

var headers = req.getAllResponseHeaders() ;

***Moderator Edit-Vidyaranjan: Updated SR details***