el-tree 第三级是横在展开

先上效果图

template

   <el-tree
              ref="roleTree"
              :check-strictly="checkStrictly"
              :render-content="renderContent"
              @node-expand="handleExpand"
              :data="routesData"
              :props="defaultProps"
              show-checkbox
              node-key="id"
              class="permission-tree"
            />

data

data(){

        return{
               checkStrictly: false,
               defaultProps: {
               children: "children",
               label: "name",  },
              routesData: [],
             }
}

methods

    handleExpand() {
      this.$nextTick(() => {
        this.changeCss();
      });
    },

    renderContent(h, { node, data, store }) {
      //树节点的内容区的渲染 Function
      let classname = "";
      // 由于项目中有三级菜单也有四级级菜单，就要在此做出判断
      if (node.level === 4) {
        classname = "foo";
      }
      if (node.level === 3 && node.childNodes.length === 0) {
        classname = "foo";
      }
      return h(
        "p",
        {
          class: classname,
        },
        node.label
      );
    },

    changeCss() {
      var levelName = document.getElementsByClassName("foo"); // levelname是上面的最底层节点的名字
      for (var i = 0; i < levelName.length; i++) {
        // cssFloat 兼容 ie6-8  styleFloat 兼容ie9及标准浏览器
        levelName[i].parentNode.style.cssFloat = "left"; // 最底层的节点，包括多选框和名字都让他左浮动
        levelName[i].parentNode.style.styleFloat = "left";
        levelName[i].parentNode.onmouseover = function () {
          this.style.backgroundColor = "#fff";
        };
      }
    },