Express.js cookie setter's Domain attribute: how to share cookie with *multiple* domains?

Let's say you have the following cookie setter:

res.cookie('name', 'tobi', {
    secure: true, 
    httpOnly: false, 
    sameSite: 'None',
    domain: '.example1.com'
});

How would you need to change the domain attribute to share the cookie with multiple domains, and not only with example1.com?

I've tried several options for the domain attribute, but none worked:

domain: "'.example1.com','example2.com'"
domain: ['.example1.com','example2.com']
domain: "['.example1.com','example2.com']"
domain: ".example1.com", domain: "example2.com"