1、使用指令

当所需功能只能通过直接的 DOM 操作来实现时，才应该使用自定义指令。可使用方法2封装成共用函数，但用指令他人复用时比较便捷。

        <el-table
          v-loading="tableLoading"
          border
          :data="tableList"
          default-expand-all
          row-key="id"
          :tree-props="{
            children: 'children',
          }"
        >
          <el-table-column
            align="center"
            label="下拉框"
            prop="selectProp"
          >
            <template #default="{ row }">
              <el-select
                v-model="row.selectProp"
                v-auto-select
                clearable
                filterable
                placeholder="请选择下拉框数据"
              >
                <el-option
                  v-for="item in select_data_source"
                  :key="item.value"
                  :label="item.label"
                  :value="item.value"
                />
              </el-select>
            </template>
          </el-table-column>
        </el-table>
<script setup>
import vAutoSelect from '@/directives/auto_select_directive'
</script>

//auto_select_directive.ts文件
import type { Directive } from 'vue'

interface ExtendedElement extends HTMLElement {
  _blurHandler?: (e: Event) => void
  _focusHandler?: (e: Event) => void
  _observer?: MutationObserver
  _currentDropdown?: HTMLElement | null
}

const vAutoSelect: Directive = {
  mounted(el: ExtendedElement) {
    const selectInput = el.querySelector('.el-input__inner')
    if (!selectInput) return

    // 精准定位当前下拉框
    const getCurrentDropdown = () => {
      const activePopper = document.querySelector(
        '.el-popper.el-select__popper[aria-hidden="false"]'
      ) as HTMLElement | null
      const selectWrapper = selectInput.closest('.el-select')
      if (activePopper && selectWrapper) {
        // 可以根据实际情况添加更多的判断条件，确保是当前 select 对应的下拉框
        return activePopper
      }
      return null
    }


    // 核心选择逻辑
    const autoSelectHandler = () => {
      const currentDropdown = getCurrentDropdown()
      if (!currentDropdown) {
        return
      }

      const visibleItems = currentDropdown.querySelectorAll<HTMLLIElement>(
        '.el-select-dropdown__item:not([style*="display: none"])'
      )

      if (visibleItems.length === 1) {
        visibleItems[0].click()
        const component = (el as any).__vueParentComponent?.ctx
        component?.handleClose?.()
      }
    }

    // 事件处理器
    const handleFocus = () => {
      el._currentDropdown = getCurrentDropdown()
    }


    const handleBlur = () => {
      autoSelectHandler()
    }


    // 智能监听器
    const initObserver = () => {
      //获取当前激活的下拉框元素
      const dropdown = getCurrentDropdown()
      if (dropdown) {
        // MutationObserver 是一个用于监听 DOM 变化的 API，它接受一个回调函数作为参数。它允许你异步地监听 DOM 的变动，如节点的添加、删除、属性的修改等，并在变动发生时执行相应的回调函数
        el._observer = new MutationObserver((mutations) => {
// mutations：一个包含所有变化记录（MutationRecord 对象）的数组。
          mutations.forEach((mutation) => {
            if (
              mutation.type === 'attributes' &&
              mutation.attributeName === 'style'
            ) {
              autoSelectHandler()
            }
          })
        })
        el._observer.observe(dropdown, {
          attributes: true, // 监听属性变化--布尔值，指示是否观察目标节点的属性变化
          attributeFilter: ['style'], // 只监听 'style' 属性的变化--字符串数组，指定要观察的属性名称
        })
      }
    }


    // 事件绑定
    selectInput.addEventListener('focus', handleFocus)
    selectInput.addEventListener('blur', handleBlur)
    el._focusHandler = handleFocus
    el._blurHandler = handleBlur

    // 初始化监听
    initObserver()
  },

  beforeUnmount(el: ExtendedElement) {
    // 清理事件
    const selectInput = el.querySelector('.el-input__inner')
    if (selectInput) {
      if (el._focusHandler) {
        selectInput.removeEventListener('focus', el._focusHandler)
      }
      if (el._blurHandler) {
        selectInput.removeEventListener('blur', el._blurHandler)
      }
    }

    // 清理 Observer
    el._observer?.disconnect()//调用 disconnect 方法可以停止观察，释放资源
    delete el._currentDropdown
  },
}

export default vAutoSelect

2、封装成共用函数

在输入文本进行搜索时，获取不到el-select内部匹配后的数据，故在失去焦点时，模拟搜索，获取筛选后的结果，当有且只有一条数据时，将那条数据赋给v-model绑定的值.

 <el-table
          v-loading="tableLoading"
          border
          :data="tableList"
          default-expand-all
          row-key="id"
          :tree-props="{
            children: 'children',
          }"
        >

          <el-table-column
            align="center"
            label="下拉框"
            prop="selectProp"
          >
            <template #default="{ row }">
              <el-select
                v-model="row.selectProp"
                clearable
                filterable
                placeholder="请选择下拉框数据"
                @blur="
                  (e) => {
                    selectSearchAuto(
                      e,
                      (newValue) => (row.selectProp= newValue),
                      select_data_source
                    )
                  }
                "
              >
                <el-option
                  v-for="item in select_data_source"
                  :key="item.value"
                  :label="item.label"
                  :value="item.value"
                />
              </el-select>
            </template>
          </el-table-column>
    </el-table>

<script setup>
  import { selectSearchAuto } from '@/utils'
</script>

//utils/index.ts文件
export function selectSearchAuto(
  event: { target: { value: string | undefined } },
  setValueCallback: (arg0: any) => void,
  dataList: any[]
) {
  const query = event.target.value?.trim()
  if (!query) return
  const filteredOptions = dataList.filter((item) => item.label.includes(query))
  if (filteredOptions.length === 1) {
    setValueCallback(filteredOptions[0].value)
  }
}

使用成本相对较高