According to this article 

<http://www.mediaevent.de/javascript/globale-lokale-variablen.html>

Global variables are in JS pretty dangerous.

I'm sorry that it's in German, but I'm gonna point out out the 2 main statements of the article.

The first is already in the 2nd paragraph of the head statement.

It says something like "In JS global var's are dangerous as they can get accessed by other scripts over the name" That's fine so far, as that's mostly the way why I want to use global var's don't I?

But in the article it sounds as this could happen randomly. and that's for sure not the expected behaving, is it?

But what is much more frightening me is the second last sentence. It forecasts that memory leaks will generated if a function that declares a 
global variable is called multiple times.
But how could this happen if the name is still the same? how there can be multiple vars declared global with the same name?
Or is this article probably written by some one just "half-knowledge"? Or maybe just addressed to some one who isn't used to the difference between global and local at all?
Or is JS really behaving in this way?

Now a concrete example:

I want some one who logs in to my page to create a Random generated token and submit it by clicking login.
on each other button I want that this token is accessed by a different function and just submit it, so that just for a new login the key will be regenerated.

For that key I was thinking about using a global variable, which gets declared by one function and gets returned by another.
But as I will generate/regenerate the key possibly more then once, would this generate memory leaks? Or is this article I'm referring to probably just dramatizing?
If this is really the way JS is behaving, what would be a good way to make a variable accessable from different functions in my case?