browser.management.onEnabled.addListener(listener)
browser.management.onEnabled.removeListener(listener)
browser.management.onEnabled.hasListener(listener)

Events have three functions:

addListener(callback)

Adds a listener to this event.

removeListener(listener)

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

hasListener(listener)

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

function

Callback function that will be called when this event occurs. The function will be passed the following argument:

info

ExtensionInfo: info about the add-on that was enabled.

Log the names of add-ons when they are enabled:

browser.management.onEnabled.addListener((info) => {
  console.log(`${info.name} was enabled`);
});