【vue-popper】 怎么使用transition属性呢？

可以这样使用：

<template>
  <vue-popper 
    transition='fade'
    enter-active-class='fade-enter-active'
    leave-active-class='fade-leave-active'
  </vue-popper>
</template>

<style>
.fade-enter-active, .fade-leave-active {
  transition: opacity 2.5s;
}
.fade-enter, .fade-leave-to {
  opacity: 0;
}
</style>

如果含有slot(带class名：container)：

.fade-enter-active,
.fade-leave-active{
    transition: opacity 200ms;
    .container{
        transition: opacity 200ms;
    }
}