The vertical property of the VTTCue interface is a string representing the cue's writing direction.
A string containing one of the following values:
"" (an empty string)Represents a horizontal writing direction.
"rl"Represents a vertical writing direction growing to the left.
"lr"Represents a vertical writing direction growing to the right.
In the following example a new VTTCue is created, then the value of vertical is set to "rl". The value is then printed to the console.
let video = document.querySelector("video");
let track = video.addTextTrack("captions", "Captions", "en");
track.mode = "showing";
let cue = new VTTCue(0, 0.9, "Hildy!");
cue.vertical = "rl";
console.log(cue.vertical);
track.addCue(cue);