how to know if someone is logged via javascript?

Question

in php i would do

if (isset($_COOKIE[\'user\']) && $_COOKIE[\'user\'] == $valueFromDb)
 echo \'logged\';

But in javascript how can

Answer 1

There is no reliable way to do this without making a request to the server, since the session might have expired on the server side. In one project, I do it the following, imperfect way:

checkAuth() {
    var logged = (function() {
        var isLogged = null;
        $.ajax({
            'async': false,
            'global': false,
            'url': '/user/isLogged/',
            'success': function(resp) {
                isLogged = (resp === "1");
            }
        });
        return isLogged;
    })();
    return logged;
}

I say imperfect because it makes a synchronous request which temporarily locks up the browser. It does have an advantage in that checkAuth() can be reliably called from any part of the client-side application since it forces the browser to wait for the result before continuing execution of the JS code, but that's about it.

The alternative, asynchronous (non-locking) approach would be to do something like this:

$.ajax({
    'url': '/user/isLogged/',
    'success': function(resp) {
        if(resp === "1") {
            // do your thing here, no need
            // for async: false  
        }
    }
});