The id property of the VTTRegion interface is a string that identifies the region.
A string that identifies the region. Initialized to an empty string when the VTTRegion object is first constructed.
In the following example, a new VTTRegion is created, then the value of id is set to "region1". The value is then printed to the console.
const region = new VTTRegion();
region.id = "region1";
console.log(region.id);