How to get Data from backend while using popupWithPost method ?

[imtechieraj]

This is my frontend code.
popupTools.popupWithPost(${profileBasePath}auth/${url}, { data: 'some data' }, "Social Profile Connect", (err, user) => { if (err) { return console.log("ERROR", err) } console.log(user) });
How I am getting this data ({ data: 'some data' }) from backend.