Is Document.cookie's setter asynchronous in web browsers?

Question

I am under the impression that document.cookie = "mySessionCookie=mySessionToken" does not get set right away in the browser.

More precisely, here's my situation:

• I am logged in.
• I want to logout using Javascript.
• So I set, for instance document.cookie = "mySessionCookie=; Path=/; Expires=Thu, 01 Jan 1970 00:00:00 GMT".
• Then I call window.location.reload() to confirm that I have been logged out.

It mostly works, but, quite often, it appears that the browser does not have enough time to set my new cookie value before calling window.location.reload().

Unless I am doing something wrong in my code, that behaviour suggests that document.cookie = "value" is not executed on the same stack (so, it might not be asynchronous by itself, but it has an unpredictable behaviour when used with the rest of the code).

So, my question is, could document.cookie = "value" be executed on a different stack?

Answer 1

Indeed, as pointed out by @charlietfl as a comment to my original question, the document.cookie setter will set the cookie right away.

My real problem was that I had an error in my program, where I was not paying attention to the fact that browsers will set the cookie's "path" based on the current URI when no path is provided along with the cookie value when setting a cookie using JavaScript.

For example, if one wants to clear a session for all URIs at example.com while viewing a resource at http://example.com/fake-resource, one must explicitly write:

document.cookie = "sessionToken=;Path=/;Expires=Thu, 01 Jan 1970 00:00:00 GMT"

else (i.e. if Path=/ is omitted) the browser will create a second cookie for example.com/fake-resource, such that the main cookie will continue to exist.