As we both are using a Mac, I am wondering what causes this incorrect display of special characters. As a long-suffering German Mac user I am used to incorrect conversion of Umlauts from Windows to Mac and vice versa, but between two Macs? Thus I'm wondering whether the UTF coding may have something to do with it.
I have no definite answer. When I look in Xcode than 'unicode (UTF-8)' is the default coding. When I look at the individual files that is also true.
But than when I open those same files with 'Texteditor' and do a 'save as...' the default coding for saving is "western (mac OS roman)". When I save them explicit with 'Texteditor' as 'unicode (UTF-8)', the default coding for saving becomes 'unicode (UTF-8)'. So I have no idea what the coding difference it between saving by Xcode or texteditor.
Self I always use "Dashcode" for editing my JS scripts. That program is part of the developer package that is on your mac installation disk, when you not already have installed it. It has an explicit option to save as a JS file. Although I can't see what coding that exactly is.
On very rare occasions I have JS files that have an unknown coding according dascode and it refuses to read them in. In that case I use texteditor to re-saving it, after which it does load.
Anyhow, try dashcode for your JS work. It even indexes all defined functions in the script in the top bar for fast finding and accessing them.