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使用vue实现级联下拉框的代码是什��

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这篇文章给大家分享的是“使用vue实现级联下拉框的代码是什么”，对大家学习和理解有一定的参考价值和帮助，有这方面学习需要的朋友，接下来就跟随小编一起学习一下吧��

�� 在前端开发中，级联选择框是经常用到的，这样不仅可以增加用户输入的友好性，还能减少前后端交互的数据量。本文以elementUI为例，使用其余UI组件大致思想也都相同��

1.数据库设��

�� 所有的相关数据皆可存在一张表中，这样数据就可以不受层级的限制��

�� 表结构可以参考如下建表SQL��

CREATE TABLE `supplies_type` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `category_type` varchar(64) NOT NULL COMMENT '类别种类：大类、中类、小��',
  `big_category_name` varchar(64) NOT NULL COMMENT '大类名称',
  `middle_category_name` varchar(64) DEFAULT NULL COMMENT '中类名称',
  `small_category_name` varchar(64) DEFAULT NULL COMMENT '小类名称',
  `parent_id` int(11) DEFAULT NULL,
  `create_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
  `create_user_name` varchar(64) DEFAULT NULL COMMENT '创建人用户名',
  `update_time` timestamp NULL DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP,
  `is_deleted` tinyint(1) DEFAULT '0' COMMENT '是否删除��1表示已删��',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4;

数据库截图如下图所示，注：本系统为了减少查询次数，故冗余了一些字段，读者可根据自己的需求调整��

核心设计在于parent_id，根据parent_id字段即可查询到子类，结果如下图所示：

2.前端页面

�� 前端页面效果如下��

Html代码如下��

<div class="app-container">
    <span style="margin-left:120px;margin-right: 20px;width: 150px;display: inline-block;">大类��</span>
    <el-select v-model="big" placeholder="请选择" @change="getSuppliesType(big)" style="width: 19%;">
      <el-option
        v-for="item in bigTypes"
        :key="item.bigCategoryName"
        :label="item.bigCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
    <span style="margin-left:120px;margin-right: 20px; width: 150px;display: inline-block;">中类��</span>
    <el-select v-model="middle" placeholder="请选择" @change="getSuppliesType(middle)" style="width: 19%;">
      <el-option
        v-for="item in middleTypes"
        :key="item.middleCategoryName"
        :label="item.middleCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
    <br>
    <br>
    <br>
    <span style="margin-left:120px;margin-right: 20px;width: 150px; margin-top:20px; display: inline-block;">小类��</span>
    <el-select v-model="small" placeholder="请选择" style="width: 19%;">
      <el-option
        v-for="item in smallTypes"
        :key="item.smallCategoryName"
        :label="item.smallCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
</div>

�� 上面的item.smallCategoryName、item.smallCategoryName数据为后端从数据库中查询出来的数据（驼峰命名），后端只负责查诀��并返回结果��

Vue中数据定义如下：

data() {
    return {
        big: '',
        bigTypes: null,
        middle: '',
        middleTypes: null,
        small: '',
        smallTypes: null
    }
},

在页面初始化时，自动获取大类列表��

created() {
		this.getSuppliesType(0)
},

页面中的getSuppliesType方法如下��

getSuppliesType(id) {
  this.listLoading = true
  const queryData = {
    parentId: id
  }
  //此处的调用后端接口按照自己的调用方式写即��
  //此处的getSuppliersType是项目中自己封装的util中的方法
  //如果请求方式是post，JSON.stringify(queryData)
  //如果请求方式是get，queryData
  getSuppliersType(JSON.stringify(queryData)).then(response => {
    console.log(response)
    console.log(response.data[0].categoryType)
    //根据type自动向三个下拉框赋��
    if (response.data[0].categoryType === 'BIG') {
      this.bigTypes = response.data
    } else if (response.data[0].categoryType === 'MIDDLE') {
      this.middleTypes = response.data
    } else {
      this.smallTypes = response.data
    }
    this.listLoading = false
  }).catch(function (error) {
    console.log(error)
    this.listLoading = false
  })
},

3.一个完整的demo

�� 下面这个页面为完成代码，其中的数据为部分数据，后台接口获取使用JS来完成��

<template>
  <div class="app-container">
    <span style="margin-left:120px;margin-right: 20px;width: 150px;display: inline-block;">大类��</span>
    <el-select v-model="big" placeholder="请选择" @change="getSuppliesType(big)" style="width: 19%;">
      <el-option
        v-for="item in bigTypes"
        :key="item.bigCategoryName"
        :label="item.bigCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
    <span style="margin-left:120px;margin-right: 20px; width: 150px;display: inline-block;">中类��</span>
    <el-select v-model="middle" placeholder="请选择" @change="getSuppliesType(middle)" style="width: 19%;">
      <el-option
        v-for="item in middleTypes"
        :key="item.middleCategoryName"
        :label="item.middleCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
    <br>
    <br>
    <br>
    <span style="margin-left:120px;margin-right: 20px;width: 150px; margin-top:20px; display: inline-block;">小类��</span>
    <el-select v-model="small" placeholder="请选择" style="width: 19%;">
      <el-option
        v-for="item in smallTypes"
        :key="item.smallCategoryName"
        :label="item.smallCategoryName"
        :value="item.id">
      </el-option>
    </el-select>
    <br>
    <br>
    <br>
    <el-button type="primary" round style="margin-left:280px" @click.native.prevent="commit">添加</el-button>
    <el-button type="primary" round style="margin-left:100px" @click.native.prevent="cancel">取消</el-button>
  </div>
</template>

<script>
    export default {
        filters: {
            parseTime(timestamp) {
                return parseTime(timestamp, null)
            }
        },
        data() {
            return {
                big: '',
                bigTypes: null,
                middle: '',
                middleTypes: null,
                small: '',
                smallTypes: null,
                dataList: [
                    {"id":1,"categoryType":"BIG","bigCategoryName":"1.现场管理与保��","middleCategoryName":null,"smallCategoryName":null,"parentId":0,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":"2021-07-04T13:34:31.000+0000","isDeleted":false},
                    {"id":27,"categoryType":"BIG","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":null,"smallCategoryName":null,"parentId":0,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":2,"categoryType":"MIDDLE","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":null,"parentId":1,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":10,"categoryType":"MIDDLE","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.2现场安全","smallCategoryName":null,"parentId":1,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":3,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.1气象监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":4,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.2地震监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":5,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.3地质灾害监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":6,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.4水文监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":7,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.5环境监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":8,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.6疫病监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":9,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.7观察测量","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":11,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.2现场安全","smallCategoryName":"1.2.1现场照明","parentId":10,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":12,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保��","middleCategoryName":"1.2现场安全","smallCategoryName":"1.2.2现场警戒","parentId":10,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":28,"categoryType":"MIDDLE","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":null,"parentId":27,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":34,"categoryType":"MIDDLE","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":null,"parentId":27,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":"2021-07-04T13:03:23.000+0000","isDeleted":false},
                    {"id":29,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.1卫生防疫","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":30,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.2消防防护","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":31,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.3化学与放��","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":32,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.4防高空坠��","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":33,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.5通用防护","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":35,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":"2.2.1生命搜索","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":36,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":"2.2.2攀岩营��","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":37,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":"2.2.3破拆起重","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":38,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":"2.2.4水下营救","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
                    {"id":39,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救��","middleCategoryName":"2.2生命搜救与营��","smallCategoryName":"2.2.5通用工具","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false}
                    ]
            }
        },
        created() {
            this.getSuppliesType(0)
        },
        methods: {
            getSuppliesType(id) {
                const queryData = {
                    parentId: id
                }
                //此处为js模拟，真实数据的获取还需要后台接口的支持
                getSuppliersType(JSON.stringify(queryData)).then(response => {
                    console.log(response)
                    console.log(response.data[0].categoryType)
                    //存放此次查询结果
                    let tmpList = []
                    this.dataList.forEach((item, index) => {
                        if(item.parentId === id){
                            tmpList.push(item)
                        }
                    })
                    if (tmpList[0].categoryType === 'BIG') {
                        this.bigTypes = tmpList
                    } else if (response.data[0].categoryType === 'MIDDLE') {
                        this.middleTypes = tmpList
                    } else {
                        this.smallTypes = tmpList
                    }
                }).catch(function (error) {
                    console.log(error)
                })
            },
            commit() {
                console.log("点击了提交按��")
            },
            cancel() {
                this.$router.go(-1)
            }
        }
    }
</script>

�� 又到了分隔线以下，本文到此就结束了，本文内容全部都是由博主自己进行整理并结合自身的理解进行总结

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