This page describes the JavaScript API that the Topology 2 View provides to allow contributed application code to integrate with, and provide additional functionality to, the topology view.
Note that this API pertains to the "Region-aware" Topology View (topo2). For the "Classic" Topology View, see here.
Topology Overlay Service
The Topology Overlay Service is a JavaScript module that provides the client-side API for registering new "topology overlay" components.