How do I get all current users from a site

Question

I need to get all currently active (not removed users) from a site. I have the following JS that gets all the users but some of them are old users that have been removed from the site (still exists in AD). How can I ensure the users returned are valid users with at least read access?

(function(){
var clientContext;
var users;

$(document).ready(function () {
    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', getUsers);
});

function getUsers() {

    var clientContext = new SP.ClientContext.get_current();
    var web = clientContext.get_web();
    var users = web.get_siteUsers();


    clientContext.load(users);
    clientContext.executeQueryAsync(RetrievedUsers, ExecutionFailed);

    function RetrievedUsers(sender, args) 
    {
        for(var i = 0; i < users.get_count();i++)
        {
            var user = users.getItemAtIndex(i);
            var name = user.get_loginName();
            alert(name);
        }
    }

    function ExecutionFailed(sender, args) 
    {
        alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
    }     
}
})();

Answer 1

Web.SiteUsers usually contains all users, that do have explicit permissions somewhere in the Web. Are you sure that there is no Point where permission inheritance is broken up and the users were granted explicit permissions?

Finally, you can´t be sure that the users you get have the permissions you want to check. You can only check permissions, which the user is assigned explicitly on. If a permission is assigned by using a AD or SP-Group the user is member of, SharePoint won´t tell you that by Default. So, after all, if you want to be sure you would have to check all the AD-Groups the user is member of too, which you would not be able to do using Javascript-CSOM.