How to migrate cookie domain and retain the value

问题

Is it somehow possible to migrate domains from a cookie? I have a trackingscript witch sets a cookie on the domain of the tracking script(server side, RoR backend) lets say mytracking.com.

The tracking script itself is integrated as javascript on the domain mycustomer.com.

Status quo is, every guest on the website mycustomer.com has now a cookie for the domain mytracking.com.

Can I somehow migrate the cookie domain from mytracking.com to mycustomer.com?

回答1:

In your client side JavaScript, generate a unique ID. Then create an iframe with a source pointing to a script on mytracking.com and the unique ID as a parameter.

var ifrm = document.createElement('iframe');
ifrm.setAttribute('src', 'mytracking.com/storecookie.rb?uuid=<UUID>');
document.body.appendChild(ifrm);

Now the storecookie.rb script can access the cookie value on the mytracking.com domain and writes it to a database along with the UUID that you generated.

Now, in your client side JavaScript, you fetch() another script, for example mytracking.com/readcookie.rb?uuid=<UUID> that retrieves the matching cookie value from the database. With the value in your client side JS, you can simply create a new cookie with the correct domain.

Unfortunately that process is a bit convoluted, but cross-domain security prevents setting a cookie for another domain.

来源：https://stackoverflow.com/questions/50856637/how-to-migrate-cookie-domain-and-retain-the-value