el-select下拉框，搜索时，若是匹配后的数据有且只有一条，则当失去焦点时，默认选中该条数据

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-tablev-loading="tableLoading"border:data="tableList"default-expand-allrow-key="id":tree-props="{children: 'children',}"><el-table-columnalign="center"label="下拉框"prop="selectProp"><template #default="{ row }"><el-selectv-model="row.selectProp"v-auto-selectclearablefilterableplaceholder="请选择下拉框数据"><el-optionv-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 | nullconst 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?.ctxcomponent?.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 = handleFocusel._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 Observerel._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-tablev-loading="tableLoading"border:data="tableList"default-expand-allrow-key="id":tree-props="{children: 'children',}"><el-table-columnalign="center"label="下拉框"prop="selectProp"><template #default="{ row }"><el-selectv-model="row.selectProp"clearablefilterableplaceholder="请选择下拉框数据"@blur="(e) => {selectSearchAuto(e,(newValue) => (row.selectProp= newValue),select_data_source)}"><el-optionv-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) returnconst filteredOptions = dataList.filter((item) => item.label.includes(query))if (filteredOptions.length === 1) {setValueCallback(filteredOptions[0].value)}
}

使用成本相对较高