data:

data(){
    return{
      timeline:[{
          type:"yellow"
      },{
         type:"blue"
      }]  
    }
}

DOM:

<li v-for="(item,idxs) in timeline" :key="idxs" :class="[$style.timeline, $style.item.type]">
    code...
</li>

expected rendering < li class= "timeline next" >
currently this dom writing method is reported to be incorrect, and the type attribute cannot be found.