Textastic only supports syntax definitions and symbol list definitions in TextMate bundles. Commands and snippets are not loaded from bundles because many of them would require a shell environment which is not available on iOS. Textastic uses its own code completion file format which could probably be used to write a code completion definition for Node.js: https://github.com/blach/Textastic-Customization

Search and Replace in Textastic for iPhone and iPad uses the NSRegularExpression class which in turn uses the syntax that is specified by ICU. 

See http://developer.apple.com/library/mac/#documentation/Foundation/Reference/NSRegularExpression_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40009708-CH1-SW53 

and 

http://userguide.icu-project.org/strings/regexp

Textastic supports the same replacement string syntax as TextMate. See http://manual.macromates.com/en/regular_expressions#replacement_string_syntax_format_strings

You can reference captures using $1, $2 etc.

Case foldings and conditional insertions are supported as described in the TextMate manual.

Another user posted a workaround here: http://feedback.textasticapp.com/topic/165187-editing-a-file-and-going-to-another-app-saves-the-file/

I still hope you make this an option :-)
For those of you that don't like the autosave option, you could turn this off just for Textastic with this command in the terminal;
defaults write com.textasticapp.textastic-mac ApplePersistence -bool no
To turn in back on use;
defaults write com.textasticapp.textastic-mac ApplePersistence -bool yes
I've testet this on DP3 of Mavericks, but it should work on Lion/ML. Found it on OSXDaily

Thanks, it will be fixed in the next update. I don't know how I missed that ;)

I've moved it to the Mac forum.

Thanks for the detailed description. The screenshots are very helpful. I'll try to fix this.

You need to escape space characters with "%20" if you reference such a file in an URL.

Can you give me details? Maybe a screenshot?

Thanks, I've forwarded this problem to the UserEcho guys: http://feedback.userecho.com/topic/211526-landscape-mode-on-ipad/