The lines property of the VTTRegion interface represents the height of the region, in number of lines.
A number representing the number of lines inside the region that cue text is rendered in. The default is 3.
In the following example, a new VTTRegion is created, then the value of lines is set to 4. The value is then printed to the console.
const region = new VTTRegion();
region.lines = 4; // Render cues in 4 lines
console.log(region.lines);