While testing UIWebView on iOS I found out there is no option to turn off JavaScript for web content. Initially I tried to use HTML5 "sandbox" attribute do achieve this, but in practice Content Security Policy is a much more flexible solution. Injecting CSP headers into NSHTTPURLResponse seems to work even for file: and data: URL schemes.
A sample application testing above solution is available on GitHub, and a similar solution has recently made its way into Onion Browser as an experimental feature. I am looking forward to see how it's going to work in practice.
On a side note, Quick Look is another solution if you need to load a single HTML document with JavaScript turned off.
