File Management in Tizen Wearable Web Widget App's Data Path for Tizen SDK 2.3.1

Question

I am working on a hybrid tizen app(web + native service) for Samsung Gear Fit2 Pro. I want to create/setup a config from web ui app and save it into data path of the app so that the native service can load the config and use it.
I am trying to create a config.txt file from tizen web app at /opt/usr/apps/pkg-id/data. I've tried using filesystem API of tizen with proper privileges but it always shows those API functions are undefined. However, if I use resolve then file creation works only for some directories like documents. But I want to create a file if not exists in my app's data folder i.e. /opt/usr/apps/pkg-id/data or modify it if already exists. Relevant portion of my code that tries to write to a file in data folder is shown below.
Is there any way to do that? Or am I doing something wrong while using the file-system api?

function app_get_datapath() {
    return "/opt/usr/apps/"+tizen.application.getCurrentApplication().appInfo.packageId+"/data/";
}

var fileHandleWrite = tizen.filesystem.openFile(app_get_datapath()+'config.txt', 'w');
fileHandleWrite.writeString(tizen.systeminfo.getCapability('http://tizen.org/system/tizenid'));
fileHandleWrite.close();

Here are the list of privileges:

Answer 1

I've tried using filesystem API of tizen with proper privileges but it always shows those API functions are undefined.

Samsung Gear Fit2 Pro does not support all new APIs. Probably you should refer to Tizen 3.0 API, but the API you use in code snippet is supported since Tizen 5.0

My second comment is that you should not use paths built 'by hand' via string concatenation as you do in app_get_datapath(). It is highly non-portable solution, which can NOT work on some devices. Instead I would suggest using built-in virtual root for getting your application private storage - wgt-private, which will automatically return valid path on a device (no matter what the device is).

Example (using only 3.0 API, for 5.0 it would be much easier):

(function createConfig() {
    function writeConfig(file) {
        file.openStream('w', function (stream) {
            stream.write(tizen.systeminfo.getCapability('http://tizen.org/system/tizenid'));
            stream.close();
            console.log('All done!!')
        })
    }

    tizen.filesystem.resolve("wgt-private/config.txt", function (file) {
        console.log('Config file exists - overwrite');
        writeConfig(file);
    }, function (e) {
        console.log('Config file does not exist - create');
        tizen.filesystem.resolve("wgt-private", function (dir) {
            var file = dir.createFile("config.txt");
            console.log("Created file")
            writeConfig(file);
        });
});
})()