Setting Cookies using JavaScript in a local html file
From the MDC page for document.cookie:
If not specified, [the
pathargument] defaults to the current path of the current document location.
So in your case, it will be /folder1/folder2/.
I didn't initially see that you'd specified "local" in the question title -- not sure if this was updated while I was writing my answer. Cookies are not set when browsing using the file:/// protocol, depending on the browser.
Browsers do not store cookies for the file:// url protocol, it will simply and silently fail to set anything at all. So if this is truly "local" and not on a domain you may have a problem.