My cookie doesn't persist between sessions?

Question

I have a cookie that saves some fairly benign data I use to check if a Changelog modal window should appear on a page or not. When I load a page there is no cookie at all. The project runs on IIS, using .NET Core 2.2 with ASP and MVC. So I do the following:

function showChangelog(override = false) {
    let newestEntryId = getNewestChangelogVersion();
    let cookieEntryId = getCookieChangelogVersion();
    if (newestEntryId > cookieEntryId) {
        setCookieDetails(false, newestEntryId);
        cookieEntryId = newestEntryId;
    }

    let changelogPersistence = getCookieChangelogPersistence();
    if (changelogPersistence === false || override === true) {
        let modalBody = $('#changelogModalBody');
        ...
        ...

Here is what happens:

• The first check returns 0. As it should. That is the newest entry in the changelog object.
• The second check returns -1. As it should. There is no cookie to check at this stage, so I return -1 to indicate this.
• Then I see if the newest entry gathered from the changelog is higher than the one from the cookie. If it is, override it and write the new version number to the cookie. That produces the following cookie:

"dontPersistChangelog=false; changelogVersion=0; path=/; expires=Tue, 06 Sep 2022 13:54:33 GMT"

• Then, from this new cookie I check whether the cookies persistence flag is true or false. If it is true, then don't show the window. If it is false, then do show the window.
• Then the code goes on to just make the window appear with all the relevant information. Sounds good.

For good measure, here is the code that sets the cookie:

/**
 * Used to set the website cookie for the changelog window.
 * @param {boolean} persistence        Whether the changelog should not persist (true) or persist (false)
 * @param {number} version             What version of the log is being put in the cookie.
 */
function setCookieDetails(persistence, version) {
    let expirationDate = new Date();
    expirationDate.setDate(expirationDate.getDate() + 999);
    let persistChangeLog = 'dontPersistChangelog=' + persistence;
    let changelogVersion = 'changelogVersion=' + version;
    document.cookie = persistChangeLog;
    document.cookie = changelogVersion;
    document.cookie = 'path =/';
    document.cookie = 'expires=' + expirationDate.toUTCString();
}

Here is the puzzling part; The actual cookie seizes to exist when I close the browser and start the browser back up. I checked using the console in the browser. It's like it gets deleted and its gone. I was under the impression that document.cookie was not the same as a session cookie? That it could persist through separate sessions?

I tried the cookie with and without an expiration date. The cookie is deleted either way. This both happens when I run the project in Visual Studio or the deployed version on my IIS.

What am I potentially doing wrong?

Answer 1

See https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie

I don't think your calls to document.cookie are updating properties of an existing cookie. A cookie's properties are semicolon separated and stored as a string.

So you set up a cookie like so:

function resetOnce() { 
   document.cookie = "doSomethingOnlyOnce=; expires=Thu,01 Jan 2050 00:00:00 GMT";
}

So for your function above:

function setCookieDetails(persistence, version) {
    let expirationDate = new Date();
    expirationDate.setDate(expirationDate.getDate() + 999);
    let persistChangeLog = 'dontPersistChangelog=' + persistence;
    let changelogVersion = 'changelogVersion=' + version;
    document.cookie = persistChangeLog + ";path =/;expires=" + expirationDate.toUTCString();
    document.cookie = changelogVersion + ";path =/;expires=" + expirationDate.toUTCString();}