tabGroups.onCreated

browser.tabGroups.onCreated.addListener(listener)
browser.tabGroups.onCreated.removeListener(listener)
browser.tabGroups.onCreated.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 created tab group's state.

Listen for and log tab group creation:

function tabGroupCreated(group) {
  console.log(
    `Tab group with ID ${group.id} was created in window ${group.windowId}.`,
  );
}

browser.tabGroups.onCreated.addListener(tabGroupCreated);