How to prevent DataTables from displaying or hiding columns on the basis of an obsolete saved state - datatables

Question

I have a table driven by DataTables 1.10. Filtering is turned on. When I talk about "doing a search" below, I'm talking about using the filtering function of this table.
Description of the Problem
Everything works fine with stateSave off. However, when stateSave is on, the following happens:
Alice logs in as admin. Because admin has all privileges, when she does a search through articles, she can see all articles. Because some articles are published and some are unpublished the table has a column that show which are published and which are not. So far so good.
Bob, a random user, accesses the site. Random users cannot ever see unpublished articles so the table hides the column that shows publication status. So far so good.
Alice logs out. She now accesses the site like a random user. So she should see exactly what Bob sees. However, when she does a search she still sees the column that indicates publication status.
(Note: The issue I'm discussing here is purely one of user interface. The server ensures that unprivileged users cannot ever get a record for an unpublished article. The problem though is that the additional column gives unpriviledged users information that they do not need. They can only see published articles in their search so they don't need to see that every article they get in a search is published.)
The code that configures the datatable hides the publication column by doing something like this:
var columnDefs = [];
if (!privileged) {
columnDefs.push({
targets: [1],
orderable: false,
visible: false
});
}
columnDefs is passed to DataTables as the columnDefs option.
Technical Reason for the Problem
The problem is that DataTables store things like column visibility into the state it saves into localStorage. So when Alice logs out and makes a search again as an unprivileged user, even though the value of columnDefs is correct, it is overwritten by the saved state. That state was stored when Alice was an admin, and it declared the publication column to be visible, so it remains visible even when Alice is accessing the site as an unprivileged user.
What I want is for users to benefit from the saved state but avoid having this state carry over when the user's privileges change.
Caveats:
I don't want to use sessionStorage because I want the state to persist between browser closings, but sessionStorage is cleared when the browser is closed.
I cannot use the session cookie assigned by the server to detect logins and logouts because it is HTTP only. Besides, privileges could change for other reasons.
I do not want to arbitrarily set an expiration time on the saved state.

Answer 1

The solution I've settled on is to use an additional field in the saved data to know when the conditions I care about have changed. This is a field whose value changes depending on the privileges that the user currently has. For instance, because in the case I described here, I decide to hide or show a column on the basis of a variable named priviledged (which is initialized from data provided by the server), it could be as simple as:
var token = privileged;
Then I set stateSaveParams to record the token when the state is saved:
stateSaveParams: function (settings, data) {
data.myapp_token = token;
}
The prefix myapp_ is just there to avoid possible collisions with DataTable's own fields.
I set stateLoadParams so that if the current value of token differs from what has been recorded before, the state is cleared:
stateLoadParams: function (settings, data) {
if (data.myapp_token !== token) {
this.api().state.clear(); // Clears the state.
return false; // Tells DataTables to not use the state that was stored.
}
// This return is here to keep the IDE happy but does not do anything special.
return undefined;
},
I've just set token to the single condition I've shown in my question (privileged) in this example but in production I use a combination of variables plus a local version number so I can bump the value of token as needed if I do something that requires clearing the state but cannot be detected just as a privilege change.