var { classes: Cc, interfaces: Ci, utils: Cu } = Components; Cu.importGlobalProperties(["File"]); var testFile = Cc["@mozilla.org/file/directory_service;1"] .getService(Ci.nsIDirectoryService) .QueryInterface(Ci.nsIProperties) .get("ProfD", Ci.nsIFile); testFile.append("prefs.js"); addMessageListener("file.open", function () { sendAsyncMessage("file.opened", { file: new File(testFile), mtime: testFile.lastModifiedTime, fileWithDate: new File(testFile, { lastModified: 123 }), fileDate: 123, }); });