There's two ways you can make use of the TelemetryTV Javascript SDK:

Type

Use Within

HTML App

Add an App to a Playlist Zone that is of the type HTML

HTML Overlay

Enable the HTML Overlay within the Overlay section of the Playlist properties.

The HTML App is like other TelemetryTV Apps in that it exists within a Playlist Page on a Zone. It is automatically created when the page is displayed and disposed of when the page is removed.

In contrast the HTML Overlay persists through-out the playback of the Playlist. It is only created when the Device starts to display the Playlist and then it is disposed when the Device restarts.