通过el-select选择器和el-tree树形结构二次封装(vue2+elementUI)，开发element-plus的TreeSelect树形选择器

在Vue 2和Element UI的环境下，可以通过自定义指令来封装一个可以使用el-select选择器和el-tree树形结构的组件。以下是一个简单的示例：

1. 创建一个Vue组件TreeSelect.vue：

<template>
  <el-popover
    ref="popover"
    placement="bottom-start"
    width="200"
    trigger="click"
    @show="$refs.tree.filter(filterText)"
  >
    <el-tree
      :data="data"
      :props="defaultProps"
      :filter-node-method="filterNode"
      ref="tree"
      @node-click="handleNodeClick"
    />
    <el-select
      slot="reference"
      :value="selectedLabel"
      @change="handleChange"
      style="width: 100%;"
      ref="select"
    >
      <el-option :value="selectedLabel" style="height: auto">
        <div :style="{ padding: '5px', width: '100%' }" @click.stop="">
          {{ selectedLabel }}
          <i slot="suffix" class="el-input__icon el-icon-arrow-down" />
        </div>
      </el-option>
    </el-select>
  </el-popover>
</template>
 
<script>
export default {
  props: {
    data: {
      type: Array,
      default: () => [],
    },
    props: {
      type: Object,
      default: () => ({
        label: 'label',
        children: 'children',
      }),
    },
    value: [String, Number],
    filterable: Boolean,
  },
  data() {
    return {
      selected: null,
      filterText: '',
      defaultProps: this.props,
    };
  },
  computed: {
    selectedLabel() {
      const node = this.data.find((d) => d[this.defaultProps.label] === this.selected);
      return node ? node[this.defaultProps.label] : '';
    },
  },
  watch: {
    value(val) {
      this.selected = val;
    },
  },
  methods: {
    handleChange(value) {
      this.$emit('input', value);
      this.$refs.popover.doClose();
    },
    handleNodeClick(data) {
      this.selected = data[this.defaultProps.label];
      this.handleChange(this.selected);
    },
    filterNode(value, data) {
      if (!this.filterable) return true;
      return data[this.defaultProps.label].indexOf(value) !== -1;
    },
  },
};
</script>

2. 在父组件中使用该组件：

<template>
  <div>
    <tree-select
      :data="treeData"
      v-model="selectedValue"
      :props="defaultProps"
      filterable
    />
  </div>
</template>
 
<script>
import TreeSelect from './TreeSelect';
 
export default {
  components: {
    TreeSelect,
  },
  data() {
    return {
      selectedValue: