Use nhost.auth.onAuthStateChanged to add a custom function that runs every time the authentication status of the user changes. E.g. add a custom function that runs every time the authentication status changes from signed-in to signed-out. 
nhost.auth.onAuthStateChanged((event, session) => {
  console.log(
    `The auth state has changed. State is now ${event} with session: ${session}`
  )
})

​
Parameters

fn required AuthChangedFunction