Add / Remove Item to/from Array via watch

demo.js

watch(arrayToWatch, (newVal, oldVal = []) => {
  const difference = newVal?.filter(x => !oldVal?.includes(x)) || [];
  console.log('difference', difference);
  
  const symmetricDifference = newVal?.filter((x) => !oldVal?.includes(x))
    .concat(oldVal?.filter((x) => !newVal?.includes(x))) || [];
  console.log('symetricDifference', symmetricDifference);
  
  if (difference?.length > 0) {
    emit('add-item', difference[0]);
  } else {
    emit('remove-item', symmetricDifference[0]);
  }
})