基于element实现select树形选择组件

<template>
    <el-select v-model="valueTitle" placeholder="请选择" :clearable="clearable" @clear="clearHandle">
        <el-option :value="valueTitle" :label="valueTitle" class="options">
            <el-tree
                    id="tree-option"
                    ref="selectTree"
                    :accordion="accordion"
                    :data="options"
                    :props="props"
                    :node-key="props.value"
                    :default-expanded-keys="defaultExpandedKey"
                    @node-click="handleNodeClick">
                <span class="custom-tree-node" slot-scope="{ node, data }">
                    <span :class="{'disable-it':node.disabled}">
                        {{node.label}}
                    </span>
                </span>
            </el-tree>
        </el-option>
    </el-select>
</template>

<script>
    //树形单选组件
    export default {
        name: "treeSelect",
        props:{
            // 配置项映射字段
            props:{
                type: Object,
                default: () => {
                    return {
                        value:'value',             // ID字段名
                        label: 'label',         // 显示名称
                        children: 'children',    // 子级字段名
                    };
                }
            },

            // 选项列表数据(树形结构的对象数组)
            options:{ type: Array, default: () => { return [] } },

            // 初始值
            value:{ type: String, default: () => { return null } },

            // 可清空选项
            clearable:{ type:Boolean, default: () => { return true } },

            // 自动收起
            accordion:{ type:Boolean, default: () => { return false } }
        },

        data() {
            return {
                valueId: null,
                valueTitle:'',
                defaultExpandedKey:[]
            }
        },
        mounted(){
            this.valueId = this.value,    // 初始值
            this.initHandle()
        },
        methods: {
            // 初始化值
            initHandle(){
                if(this.valueId){
                    setTimeout(() => {
                        this.valueTitle = this.$refs.selectTree.getNode(this.valueId)?.data[this.props.label]     // 初始化显示
                        this.$refs.selectTree.setCurrentKey(this.valueId)       // 设置默认选中
                        this.defaultExpandedKey = [this.valueId]      // 设置默认展开
                    }, 500);
                } else {
                    this.valueTitle = ""
                }
                this.initScroll()
            },

            // 初始化滚动条
            initScroll(){
                this.$nextTick(()=>{
                    let scrollWrap = document.querySelectorAll('.el-scrollbar .el-select-dropdown__wrap')[0]
                    let scrollBar = document.querySelectorAll('.el-scrollbar .el-scrollbar__bar')
                    scrollWrap.style.cssText = 'margin: 0px; max-height: none; overflow: hidden;'
                    scrollBar.forEach(ele => ele.style.width = 0)
                })
            },
            // 切换选项
            handleNodeClick(node, obj){
                if(node.disabled) return false;
                // if(obj.level <= 1 ) return false
                this.valueTitle = node[this.props.label]
                this.valueId = node[this.props.value]
                this.$emit('getValue', [this.valueId,this.valueTitle])
                this.defaultExpandedKey = []
            },
            // 清除选中
            clearHandle(){
                this.valueTitle = ''
                this.valueId = null
                this.defaultExpandedKey = []
                this.clearSelected()
                this.$emit('getValue', [this.valueId,this.valueTitle])
            },

            // 清空选中样式
            clearSelected(){
                let allNode = document.querySelectorAll('#tree-option .el-tree-node')
                allNode.forEach((element)=>element.classList.remove('is-current'))
            }

        },

        watch: {
            value(){
                this.valueId = this.value
                this.initHandle()
            }
        },
    }
</script>

<style scoped>
    .el-scrollbar .el-scrollbar__view .el-select-dropdown__item{
        height: auto;
        max-height: 274px;
        padding: 0;
        overflow: hidden;
        overflow-y: auto;
    }
    .el-select-dropdown__item.selected{
        font-weight: normal;
    }
    ul li >>>.el-tree .el-tree-node__content{
        height:auto;
        padding: 0 20px;
    }
    .el-tree-node__label{
        font-weight: normal;
    }
    .el-tree >>>.is-current .el-tree-node__label{
        color: #409EFF;
        font-weight: 700;
    }
    .el-tree >>>.is-current .el-tree-node__children .el-tree-node__label{
        color:#606266;
        font-weight: normal;
    }
   .el-tree >>> .disable-it {
        color: #aca8a8;
    }
</style>