隐藏element-ui中tree懒加载叶子节点checkbox（分页懒加载效果）

根据最新的工作需求中指示，要求Tree树组件为lazy懒加载，且能够进行复选框选择，这个实现简单，设置show-checkbox即可，若此处要求叶子节点也不能包含复选框，就有些困扰了

1. 首先按照官网，拷贝tree树组件代码，设置完show-checkbox，图中查看更多为叶子节点，且设置数据节点属性为disabled

<el-tree
      ref="treeRef"
      class="treeDom"
      lazy
      :show-checkbox="showCheckbox"
      :props="defaultProps"
      highlight-current="true"
      :check-strictly="true"
      :load="lazyLoadMore"
      :expand-on-click-node="false"
      :default-expanded-keys="defaultExpandKeys"
      :default-checked-keys="defaultCheckedKeys"
      node-key="id"
      @node-expand="handleNodeExpand"
      @node-collapse="handleNodeCollapse"
      @node-click="handleNodeClick"
      @check="handleCheck"
    >
      <div slot-scope="{ node, data }" class="custom-tree-node">
        <!-- 查看更多 -->
        <span
          v-if="data.id ==='loadmore'"
          class="tree-node loadmore"
          @click="loadMoreNode(node,data)"
        >
          <el-link>{{ node.label }}</el-link>
        </span>
        <!-- 数据到底了 -->
        <span
          v-if="data.id ==='disabledload'"
          class="tree-node no-data"
          style="color: #999; cursor: auto;"
        >
          {{ node.label }}
        </span>
        <!-- 普通节点 -->
        <el-tooltip
          class="item"
          effect="light"
          placement="right-start"
        >
          <div slot="content" style="max-width: 300px;">
            {{ node.label }}
          </div>
          <span v-if="data.id !=='loadmore' && data.id!=='disabledload'" class="span-tree-node" @click="loadMoreNode(node,data)">{{ node.label }}</span>
        </el-tooltip>
      </div>
    </el-tree>

css样式如下：

::v-deep .span-tree-node {
  width: 120px;
  position: absolute;
  text-overflow: ellipsis;
  overflow: hidden;
  color: #696969;
  top: 50%;
  transform: translateY(-50%);
}

::v-deep .treeDom {
  width: 100%;
  overflow-x: auto;

  .custom-tree-node {
    width: 100% !important;
    position: relative;
  }

  .el-tree-node {
    .el-tree-node__expand-icon + label {
      display: none;
    }

    &.is-expanded {
      .is-leaf + label {
        display: none !important;
      }
    }

    & > div:nth-last-of-type(2) { // 有children的节点,反推父节点展示可选
      .el-tree-node__expand-icon + label {
        display: block;
      }
    }
  }
}

2. 由于属性是isleaf，所以lazy状态下叶子节点不会有加载目录符号，但此时，有个禁用复选框，现在只需要对它设置样式即可

::v-deep .el-tree .el-tree-node:last-child {
  .el-tree-node__content .is-leaf +.el-checkbox.is-disabled{
    display: none;
  }
  .el-tree-node__content.is-not-clickable{
    cursor: pointer;
  }
}

3. 分页懒加载实现功能也比较简单，可以复写tree树自带的load方法，load方法内默认携带两个返回参数，一个是node，一个是resolve，即懒加载数据必须是通过resolve就是return 将数据带回，在自定义调用load方法时，多添加了parentNode第二次以上堆积的数据，以及childNode 上一页最后一个option Node节点

  async lazyLoadMore(node, resolve, parentNode = [], childNode) {
     let id = node?.data?.id, pre = childNode ? childNode.data.name : (node?.data?.name), data = [], arrId = '';
      if (node.level === 0) {
        id = this.paramNode.parent;
        pre = '';
        return resolve([{id: id, name: id, leaf: false, disabled: false}]);
      }
      if (node.level === 1 && !childNode) {
        pre = '';
      }
      
      // 节点各自的resolve
      let result = this.funcResolve.findIndex(ele => ele.node === node);
      if (result < 0) {
        this.funcResolve.push({node, resolve});
      }

      // 判断获取分页查询的pre参数
      if (id && id.indexOf('/') > -1) {
        let arrIndex = id.lastIndexOf('/') + 1;
        arrId = id.substring(arrIndex);
        if (arrId === pre) pre = '';
      }
      // lazy加载查询接口
      const { data: {items} } = await getInterfaceTreeDictory({parent: id || '', pre: pre || '', pageSize: this.pageSize});
      data = items.map(({interface_url: name, full_interface_url: id, disabled = false}) => {
        return {name, id, disabled};
      });

      // 翻页信息添加
      if (data.length >= this.pageSize) {
        let nearName = data[data.length - 1].name;
        data.push({name: '查看更多', id: 'loadmore', nearName: nearName, leaf: true, disabled: true});
      }

      // 查看更多加载需根据各自的resolve加载数组数据
      if (parentNode && parentNode.length > 0) {
        parentNode.push(...data);
        return resolve(parentNode);
      } else {
        return resolve(data);
      }
    },

    // 查看更多事件点击
    loadMoreNode(node, data) {
      if (data.id === 'loadmore') {
        let nodeParentKey = node.parent.key ? node.parent.key : this.paramNode.parent;
        let childNode = {
            data: {
              id: nodeParentKey,
              name: data.nearName
            }
          }, resolve = '';
        let parentNode = node.parent.childNodes.map(({key: id, label: name, disabled})=>{
          return { name, id, disabled };
        });
        // 剔除自定义查看更多option数据
        if (parentNode.length > 0) {
          parentNode = parentNode.slice(0, -1);
        }

        // 选取resolve返回
        if (parentNode.length <= this.pageSize * this.pageNumber) {
          resolve = this.funcResolve.filter((item)=>{
            return item.node === node.parent;
          });
          this.pageNumber++;
          // 调用原生Tree load方法
          this.$refs.treeRef.load(node.parent, resolve[0].resolve, parentNode, childNode);
        }
      }
    },

代码内有一点需要注意，即每次查询接口的时候，和后台约定的规则是：不包含分页，需要传值两个参数，一个是parent，即当前节点的上一级所有层级拼接，另一个是pre即当前节点的子集，若第一次加载，pre可为空，若查看更多再一次加载pre为上一次加载数据data的最后一个元素id，作为传参；

eg: a、此时需要点击加载js，即 GET请求下param参数如下parent=172.24.114.143:8080/js&pre=

b、此时继续点击查看更多，则传入parent=172.24.114.143:8080/js&pre=jquery-showloading

4. 到此代码和效果都正常了，感觉不错的话，给个关注和点赞吧~如有需要可私聊