Javascript or Java?

I've been learning Python recently in order to use API and produce some of my own projects. However, I am interested in security vulnerabilities and hacking using some of these scripting languages in order to gain a better understanding.

What would you advise, Javascrpt or Java? - In general. No specifics.

Also, best methods or next best direct to take this with: learning, developing and scripting? I.e. materials or learning tutorials available?

Thanks.