1.第一种
<button @click="setState(0)" :class="{active:state===0}">按钮</button>
2.第二种
<div class="control" :class="{play: !play, pause: play}" @click="clickControl"></div>
play:true
3.第三种
<div :class="['picDiv',item.selected?'divSelected':'']" @click="setStyleToPic">
.picDiv{
  width: 64px;
  height:64px;
  float: left;
  img{
    width: 64px;
    height: 64px;
  }
  &.divSelected{
    width: 72px;
    height:72px;
    img{
      width: 72px;
      height: 72px;
    }
  }
}
4.第四种
<div :class="[rightBtnIsSelected?'yes':'no','nextImg']"></div>
.nextImg{
  cursor: pointer;
  position: absolute;
  bottom: $turn-logo-bottom;
  right: $turn-logo-right;
  pointer-events: auto;
  &.yes{
    
  }
  &.no{
   
  }
}