点击下拉旋转，二次点击恢复(vue写法)

/* 动画 */
.downIcon {
  transform: rotate(0deg) !important;
  -webkit-transition: transform 0.25s linear;
  -moz-transition: transform 0.25s linear;
  -o-transition: transform 0.25s linear;
  transition: transform 0.25s linear;
}
.iconTrans {
  transform: rotate(180deg) !important;
  -webkit-transition: transform 0.25s linear;
  -moz-transition: transform 0.25s linear;
  -o-transition: transform 0.25s linear;
  transition: transform 0.25s linear;
}

 <img src="./img/icon-down.svg" :class="{ downIcon: true, iconTrans: this.isShowOption1 }"/>