nsIMIMEService getFromTypeAndExtension(/*string*/aMimeType,/*string*/aFileExt) return nsIMIMEInfo getPrimaryExtension(/*string*/aMIMEType,/*string*/aFileExt) return mimeTypeString getTypeFromExtension(/*string*/aFileExt) return mimeTypeString getTypeFromFile(/*nsIFile*/aFile) なんか使えない getTypeFromURI(/*nsIURI*/ aURI) return mimeTypeString Example var fileName = "foo.tar.gz"; var mts = Cc["@mozilla.o