Transition プロパティ

{
  name: 'page',
  mode: 'out-in'
}

export default {
  pageTransition: 'page'
  // or
  pageTransition: {
    name: 'page',
    mode: 'out-in',
    beforeEnter (el) {
      console.log('Before enter...');
    }
  }
}

{
  name: 'layout',
  mode: 'out-in'
}

export default {
  layoutTransition: 'layout'
  // or
  layoutTransition: {
    name: 'layout',
    mode: 'out-in'
  }
}

.layout-enter-active,
.layout-leave-active {
  transition: opacity 0.5s;
}
.layout-enter,
.layout-leave-active {
  opacity: 0;
}