设置el-tooltip的宽度

   <div class="title" >
              <el-tooltip v-bind:content="item.content" popper-class="tips" placement="bottom" effect="light">
                <a href=""> {{item.message}}</a>
              </el-tooltip>
            </div>    

<el-tooltip placement="top">
  <div slot="content">多行信息<br/>第二行信息</div>
  <el-button>Top center</el-button>
</el-tooltip>