如何在同步函数中等待JavaScript中的异步调用?

I recently had to correct security issues in a web-application (that I didn't create). The security problem was, it was using non-http-only cookies. So I had to set the session-cookie http-only, which means you can't read (and set) the cookie's value anymore from javascript. So far so seamingly easy. I recently had to correct security issues in a