element 表格内容过长时设置隐藏，通过popover弹窗显示

<el-table-column prop="safetyRisk" label="安全隐患" width="200">
    <template slot-scope="scope">
          <el-popover
            placement="top-start"
            title="安全隐患"
            width="300"
            trigger="hover"
          >
            <div>{{ scope.row.safetyRisk }}</div>
            <span slot="reference">{{
              scope.row.safetyRisk.substr(0, 30) + "..."
            }}</span>
          </el-popover>
    </template>
</el-table-column>