Why document.cookie is not working

Try using jQuery Cookie plugin:

jQuery Cookie plugin

$.cookie('the_cookie', 'the_value', { expires: 7, path: '/' });

Sometimes this can occur if the page is hosted on a domain listed on the public suffix list (e.g. github.io, cloudfront.net). These domains are treated specially by the browser and restrict writing cookies for security reasons.

See here for a Live Example

You're using ; instead of ,.

Use , to deliminate your cookie values

var curCookie = name + "=" + value + 
    ", expires=" + ATS_getExpire() + 
    ", path=" + path + 
    ", domain=" + domain;

document.cookie = curCookie;
alert("Your Cookie : " + document.cookie);

UPDATE

As of today (2021-08-25), the live example is not consistent accross browsers:

• Chrome 92.0.4515.159: ❌
• Edge 92.0.902.78: ❌
• Opera 77.0.4054.277: ❌
• Firefox 91.0.2: ✅

I found that ... frustratingly, document.cookie doesn't work when running the page locally in one's browser.

When I uploaded the same page to a website, suddenly all the cookie values worked just fine. I will find out why this is and fill the rest of this answer out later.