vue 基于elment UI tree 组件实现带引导、提示线

准备工作，先实现 树状组件的基本样式

<span style="height:500px; display:block; overflow-y:auto;" class="mytree">
        <el-tree
          :data="data"
          show-checkbox
          :indent="0"
          node-key="id"
          :default-expand-all="true"
          :props="defaultProps"
        ></el-tree>
      </span>

　　

　接下来修改css ，注：indent 设置为零，不然线与节点间的间隙会比较大， 我使用的是 scss，less 也行

.mytree /deep/ {
    .el-tree > .el-tree-node:after {
      border-top: none;
    }
    .el-tree-node {
      position: relative;
      padding-left: 16px;
    }
    //节点有间隙，隐藏掉展开按钮就好了,如果觉得空隙没事可以删掉
    .el-tree-node__expand-icon.is-leaf {
      display: none;
    }
    .el-tree-node__children {
      padding-left: 16px;
    }

    .el-tree-node :last-child:before {
      height: 38px;
    }

    .el-tree > .el-tree-node:before {
      border-left: none;
    }

    .el-tree > .el-tree-node:after {
      border-top: none;
    }

    .el-tree-node:before {
      content: '';
      left: -4px;
      position: absolute;
      right: auto;
      border-width: 1px;
    }

    .el-tree-node:after {
      content: '';
      left: -4px;
      position: absolute;
      right: auto;
      border-width: 1px;
    }

    .el-tree-node:before {
      border-left: 1px solid #c0c4cc;
      bottom: 0px;
      height: 100%;
      top: -26px;
      width: 1px;
    }

    .el-tree-node:after {
      border-top: 1px solid #c0c4cc;
      height: 20px;
      top: 12px;
      width: 24px;
    }
  }

　　完，大功告成！