I was tweaking out on your code and I have it successfully adding the correct extension based on if it’s a .js or .css file (initially all files are saved with .js extension)

Also, the original code re-writes the file names with the original file extension still intact (eg. styles.css.min.css or scripts.js.min.js). This is fixed now. Here is the working code.

[code]
on run
tell application "Finder"
set this_item to choose file with prompt "Choose CSS or JS file:"
set dir to the selection as alias
set dir to container of dir as text
set ext to name extension of this_item
set newName to this_item as text
set newName to text 1 thru ((offset of "." & ext in newName) - 1) of newName

end tell
set newPath to posix_path(newName)
set mypath to posix_path(this_item)
set dirpath to posix_path(dir)

runCompression(mypath, dirpath, newPath, ext)
end run

on posix_path(mac_path)
set mac_path to (mac_path as text)
set root to (offset of ":" in mac_path)
set rootdisk to (characters 1 thru (root - 1) of mac_path)
tell application "Finder"
if (disk (rootdisk as string) is the startup disk) then
set unixpath to "/" & (characters (root + 1) thru end of mac_path)
else
set unixpath to "/Volumes:" & mac_path
end if
end tell
set chars to every character of unixpath
repeat with i from 2 to length of chars
if item i of chars as text is equal to "/" then
set item i of chars to ":"
else if item i of chars as text is equal to ":" then
set item i of chars to "/"
else if item i of chars as text is equal to "'" then
set item i of chars to "\'"
else if item i of chars as text is equal to """ then
set item i of chars to "\" & """
else if item i of chars as text is equal to "*" then
set item i of chars to "\*"
else if item i of chars as text is equal to "?" then
set item i of chars to "\?"
else if item i of chars as text is equal to " " then
set item i of chars to "\ "
else if item i of chars as text is equal to "\" then
set item i of chars to "\\"
end if
end repeat
return every item of chars as string
end posix_path

on runCompression(mypath, dirpath, newPath, ext)
tell application "Terminal"
do shell script "java -jar " & dirpath & "yuicompressor-2.4.2.jar " & mypath & " -o " & newPath & ".min." & ext
end tell
end runCompression [/code]

– geoff