I'm bad at Javascript. When using Artstation, it will prompt me to log in. I don't want to.

In their main.6dd57cc2a9e0f72b4453.js script, there is the check:

            t.prototype.isSignedIn = function() {
                return !!this.id
            }

If I put a breakpoint there, then exectute this.id = 1 in the console, it works. Can this be done automatically? I do have GreaseMonkey, but just letting this.id = 1 run at site load doesn't work, because this is something completely else when it runs.