setting cross-subdomain cookie with javascript

Question

How should I add domain support to these functions? I want to achieve that .example.com is declared as domain, so that the cookies can be read across all subdomains of the example.com. In its current form since domain is not set, it can only be read from www.example.com

Answer 1

Here is a link on how to share cookies amongst a domain:

https://www.thoughtco.com/javascript-by-example-2037272

It involves setting the domain attribute of the cookie string like:

document.cookie = "myValue=5;path=/;domain=example.com";

This cookie should now be accessible to all sub domains of example.com like login.example.com

Answer 2

In my case we needed to set a cookie that would work across our .com subdomains:

function setCrossSubdomainCookie(name, value, days) {
  const assign = name + "=" + escape(value) + ";";
  const d = new Date();
  d.setTime(d.getTime() + (days*24*60*60*1000));
  const expires = "expires="+ d.toUTCString() + ";";
  const path = "path=/;";
  const domain = "domain=" + (document.domain.match(/[^\.]*\.[^.]*$/)[0]) + ";";
  document.cookie = assign + expires + path + domain;
}

This might not work for .co.uk etc but the principle can be used