Here your solution:

var myDocument = app.documents.item(0);

var myPage = myDocument.pages.item(0);

var myTextFrame = myPage.textFrames.item(0);

var myTextObject = myTextFrame.parentStory.characters.item(0);

main ();

function main ()

{

try

{

if (app.selection[0].parentStory.storyPreferences.storyDirection == StoryDirectionOptions.rightToLeftDirection)

app.selection[0].parentStory.storyPreferences.storyDirection = StoryDirectionOptions.leftToRightDirection

else

app.selection[0].parentStory.storyPreferences.storyDirection = StoryDirectionOptions.rightToLeftDirection

}

catch (_){}

}