tabGroups.onRemoved

browser.tabGroups.onRemoved.addListener(listener)
browser.tabGroups.onRemoved.removeListener(listener)
browser.tabGroups.onRemoved.hasListener(listener)

Events have three functions:

addListener(listener)

Adds a listener to this event.

removeListener(listener)

Stops listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Checks whether listener is registered for this event. Returns true if it is listening, false otherwise.

listener

The function called when this event occurs. The function is passed this argument:

group

tabGroups.TabGroup. Details of the removed tab group's state.

removeInfo

object. Information on why the tab group is closing.

isWindowClosing

boolean. true if the tab group is removed because its window is closing.

Listen for and log tab group removals:

function tabGroupRemoved(group) {
  console.log(`Tab group with ID ${group.id} was removed.`);
}
browser.tabGroups.onRemoved.addListener(tabGroupRemoved);