windows.onBoundsChanged

browser.windows.onBoundsChanged.addListener(listener)
browser.windows.onBoundsChanged.removeListener(listener)
browser.windows.onBoundsChanged.hasListener(listener)

Events have three functions:

addListener(listener)

Adds a listener to this event.

removeListener(listener)

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

hasListener(listener)

Check whether a 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:

window

A windows.Window object containing details of the window that was resized or moved.

Log the IDs of windows that are moved or resized:

browser.windows.onBoundsChanged.addListener((window) => {
  console.log(`New window: ${window.id}`);
});