优雅的将ElementUI表格变身成树形表格的方法步骤

<template>
 <div>
  TreeTable
  <el-table :data="list" :row-style="tableRowStyle" border>
   <el-table-column type="selection" width="55"></el-table-column>
   <el-table-column prop="id" label="ID" width="180">
    <template slot-scope="scope">
     <span class="collapse"
        :class="collapseClass(scope.row)"
        :style="tableRowPaddingStyle(scope.row)"
        @click="handleCollapseClick(scope.row)">
     </span>
     <span>{{ scope.row.id }}</span>
    </template>
   </el-table-column>
   <el-table-column prop="name" label="NAME"></el-table-column>
  </el-table>
 </div>
</template>

<script lang="ts">
  import {Component, Vue} from 'vue-property-decorator'
  // 引入两个封装好的工具方法
  import { arrayToTree } from './utils/array.js'
  import { ergodicTree } from './utils/tree.js'

  @Component
  export default class TreeTable extends Vue {
    private list: object[] = [];
    private tree: object[] = [];

    created() {
      // 准备一组含有父子级关系的一维数组方便示例测试
      // 在实际项目应用中，理应通过后端接口返回
      let _list = [
        {
          id: 'a',
          pid: '',
          name: '部门a',
          children: []
        },
        {
          id: 'a1',
          pid: 'a',
          name: '子部门a1',
          children: []
        },
        {
          id: 'a2',
          pid: 'a',
          name: '子部门a2',
          children: []
        },
        {
          id: 'a2-1',
          pid: 'a2',
          name: '子部门a2-1',
          children: []
        },
        {
          id: 'a2-2',
          pid: 'a2',
          name: '子部门a2-2',
          children: []
        },
        {
          id: 'a3',
          pid: 'a',
          name: '子部门a3',
          children: []
        },
        {
          id: 'a3-1',
          pid: 'a3',
          name: '子部门a3-1',
          children: []
        },
        {
          id: 'b',
          pid: '',
          name: '部门b',
          children: []
        },
        {
          id: 'b1',
          pid: 'b',
          name: '子部门b1',
          children: []
        },
        {
          id: 'c',
          pid: '',
          name: '部门c',
          children: []
        },
      ];
      
      // 将一维数组转成树形结构并存储于tree变量
      this.tree = arrayToTree(_list);
      
      // 考虑到实际应用过程中接口返回的数据是无序的，所以我们对tree进行先序遍历将节点一一插入到list变量
      this.list = [];
      ergodicTree(this.tree, (node: any) => {
        this.list.push(node);
        
        // 遍历过程中并对每个节点挂载open和show属性
        // open：控制节点的打开和关闭
        // show：控制节点的显示和隐藏
        this.$set(node, 'open', true);
        this.$set(node, 'show', true)
      })
    }

    // 控制行的显示和隐藏
    tableRowStyle(scope: any) {
      return {
        'display': scope.row.show ? '' : 'none'
      }
    }

    // 通过每个节点的深度，设置行的缩进实现视觉上的层级效果
    tableRowPaddingStyle(row: any) {
      return {
        'margin-left': `${(row._depth - 1) * 24}px`
      }
    }

    // 控制展开按钮的展开和关闭状态
    collapseClass(row: any) {
      return {
        'collapse--open': row.open == false && row.children && row.children.length > 0,
        'collapse--close': row.open == true && row.children && row.children.length > 0
      }
    }

    // 处理展开按钮的点击事件
    handleCollapseClick(row: any) {
      const _open = row.open;
      // 通过节点访问路径控制节点的显示隐藏，由于内存指针的关系list和tree的节点操作都会相互影响
      ergodicTree(this.tree, (node: any) => {
        node._idPath.forEach((pathId: any) => {
          if (pathId == row.id) {
            this.$set(node, 'show', !_open);
            this.$set(node, 'open', !_open)
          }
        })
      });
      row.show = true;
      row.open = !_open;
    }
  }
</script>

<style lang="scss" scoped>
 .collapse {
  display: inline-block;
  width: 8px;
  cursor: pointer;
  margin-right: 8px;
 }

 .collapse--open:before {
  content: '+';
 }

 .collapse--close:before {
  content: '-';
 }
</style>

export function arrayToTree(list: object[], props = {id: 'id', pid: 'pid', children: 'children'}) {
      let tree: object[] = [];
      let map: any = {};

      let listLength = list.length;
      for (let i = 0; i < listLength; i++) {
        let node: any = list[i];
        let nodeId: any = node[props.id];
        map[nodeId] = node;
      }

      for (let i = 0; i < listLength; i++) {
        let node: any = list[i];
        let nodePid: any = node[props.pid];
        let parentNode: any = map[nodePid];
        if (parentNode) {
          parentNode[props.children] = parentNode[props.children] || [];
          parentNode[props.children].push(node)
        } else {
          tree.push(node)
        }
      }

      return tree
    }

export function ergodicTree(tree: object[], callback: any = () => {}, props = {id: 'id', pid: 'pid', children: 'children'}) {
      function _ergodicTree(tree: object[], parentIdPath?: any[], depth: number = 0) {
        const treeLength = tree.length;
        for (let i = 0; i < treeLength; i++) {
          let node: any = tree[i];
          const _idPath: any[] = parentIdPath ? [...parentIdPath, node[props.id]] : [node[props.id]];
          const _depth: number = depth + 1;
          node._idPath = _idPath;
          node._depth = _depth;
          callback(node);
          if (node[props.children] && node[props.children] instanceof Array) {
            _ergodicTree(node[props.children], _idPath, _depth)
          }
        }
      }

      _ergodicTree(tree);
      return tree;
    }