[Vuejs]-Watch array inside array of objects

When you want to watch nested data (array or object) you need to set deep to true in you watcher.

I encourage you to read the official Vuejs doc about watcher : https://v2.vuejs.org/v2/api/#watch

In your case you would have something like that :

watch: {
  element: {
    deep: true,
    handler: function (val, oldVal) {
      console.log('updated')
    }
  }
}