vue实现长图垂直居上 vue实现短图垂直居中

<div class="box" v-for="item in previewImg">
  <img :src="item" alt="" @load="checkHeight($event)">
</div>

.box{
 height: 100%;//如高度等于网页高度
 overflow: auto;
 display: flex;
 flex-direction: column;
 justify-content: space-around;
}
.swiper-slide.long{
 justify-content: flex-start;
}

methods: {
checkHeight:function (event) {
  var el=$(event.currentTarget);
  el.parent().removeClass('long');
　　//this.CH 为网页高度
  if(el.height()>this.CH){
    el.parent().addClass('long');
  }

}

}