Using an alias within a condition before it has been registered

[teststack-git]

Is there a way to utilize aliases in a condition? In essence, I am attempting generate a token and store it as an alias, however I only want to generate the token if the alias does not yet exist. I'm looking to implement something like this or similar:

if(cy.get('@tokenAlias')===null) { do something }

The obvious problem is that '@tokenAlias' has not been defined and hence throws an alias not registered error.