How can I prevent javascript code theft?

Actually I’m developing a Chrome extension and a jQuery plugin to upload it and sell it on Codecanyon. When I “Inspect source” of the page and I click on the “Resources” tab, the javascript file looks empty. How does Codecanyon do that? I want to have file theft prevention in my own website too, but I don’t know how to do it. I know php and javascript and there’s no method to do it, because the browser downloads the file to execute it.

You can see the example here.

Answer

You can only try to make it less readable (through minifiaction and obfuscation), but the code is still tranferred and it can be reverse engineered.

The actual code in your example is downloaded with the jquery.js file.