The codepen you provided uses Vue 2. Your question is tagged Vue 3, so I assume you are using Vue 3. Vue 3 made changes to transition class ... ... <看更多>

We're sorry but vue-codepen doesn't work properly without JavaScript enabled. Please enable it to continue. HTML; CSS; JS. Result; Skip Results Iframe. ... <看更多>

GitHub - ivanvermeyen/vue-collapse-transition: Custom Vue transition to collapse elements ... You can find a quick demo to play with on CodePen. ... <看更多>

But I like to use Vue JS because it simplifies some things. You like this video? ... GitHub (https://github.com ... ... <看更多>