Code :
 var formData = ({first_name:firstname,last_name:lastname,user_name:username, email:email,password:password});
  request.post({url:'http://localhost:8081/register', JSON: formData}, function(err, connection, body) {
exports.Register = function(req, res) {
    res.header("Access-Control-Allow-Origin", "*");
    console.log("Request data " +JSON.stringify(req));
This is a request package for node.js. But I am getting this error in return:
TypeError: Converting circular structure to JSON
Can someone help me with this?