Hey Gerhard, 

you can find the Create token endpoint documentation here :

https://docs.safe.com/fme/html/FME_REST/apidoc/v3/#!/tokens/createForm

I can't help you with the javascript part though.

I want to create Session Token and not api Token. The documentation does not explain, which Token will be created. I need an JavaScript example. In the Safe JavaScript examples they use an older deprecated api. Perhaps there is an fme developer forum.

After some testing and digging, I found that the trick to create a session token instead of an API token is to add the s=1 parameter:

http://FMEFLOWURL/fmerest/v3/tokens/?s=1

The rest of the request remains the same.