.example-enter {
  opacity: 0.01;
  transition: opacity 1s ease-in;
}

.example-enter.example-enter-active {
  opacity: 1;
}

.example-leave {
  opacity: 1;
  transition: opacity 1s ease-in;
}

.example-leave.example-leave-active {
  opacity: 0.01;
}

.item {
  width:100px;
  border:1px solid red;
  padding:10px;
  margin:10px;
}