Listen for events source elsewhere in the lineup.
The message event is fired on a Window object when the window receives a message from another browsing context.
A work in progress LISTEN registers for and reports the arrival of a specific event.
LISTEN hello
LISTEN registers as a handler of "message" events via window.addEventListener. Messages with action publishSourceData are handled so long as either field name or field topic match that specified as the way to listen. Use MESSAGE as one possible source for compatible events.