Ways to make Javascript code hacking / injection / manipulation difficult?

Question

Are there ways to prevent, or make it difficult enough, for someone to inject Javascript and manipulate the variables or access functions? A thought I had is to change all var names randomly on each reload so the malware script would need to be rewritten every time? Or are there other less painful ways?

I understand that eventually someone will hack his way in, but I'd like to know ways to make it difficult to reproduce the action, so that people won't publish a bookmarklet or something similar for everyone to use. I don't care if experts find their way in the code, but I'd like it to be a bit more complex than javascript:d=0;

If you know ways to make hacking Javascript a bit more difficult, please write those.

Answer 1

Accept that your javascript will be "manipulated" and make provision at the server side. There's fundamentally nothing you can do to stop people tinkering with the client.