el-tooltip 

• 判断文本超出显示...时，显示tooltip

handleShowTooltip(event) {
    let cell = event.target.querySelector('.el-tooltip')
    this.showTooltip =
    cell.scrollWidth === cell.offsetWidth &&
    cell.scrollHeight === cell.offsetHeight
}


<div  
@mouseenter="handleShowTooltip($event)" 
class="listInfo" 
v-for="(line,index)in item.lines" >          
     <el-tooltip :disabled="showTooltip" effect="dark" popper-class="toolTipClass":content="line.line" placement="top" >
         <div style="white-space:pre" class="content" :class="{blue:line.isApplyLog==1}">{{line.line}}</div>
      </el-tooltip>
</div>

• 自定义class

 popper-class="toolTipClass"