<select class="select" v-on:change="indexSelect($event)" v-model="pcNum">
	<option v-for="(item, index) in pcArr" :key="index" v-bind:value="item.pcNum">{{ item.pcNum }}</option>
</select>

js：

data() {
		return {
			pcNum:'PC20200924',
			pcArr:[
					{id:1, pcNum: 'PC20200924'},
					{id:2, pcNum: 'PC20200925'},
					{id:3, pcNum: 'PC20200926'}
			],
        }
 },
 methods:{
     indexSelect(e){
         console.log(e)
         console.log(e.target.selectedIndex) // 选择项的index索引
         console.log(e.target.value) // 选择项的value，也就是v-bind:value 的绑定值，如果换成 v-bind:value="item.id",则打印的是 选中项的id
     }
 }

扩展：获取下拉框选中项的其他值，如选中蓝色妖姬时获取它的英文名 bluerose

<select class="select select2" @change="classSelect($event)"  v-model="classs">
	 <option v-for="(item, index) in classsArr" :key="index" v-bind:value="item.name">{{ item.name }}</option>
</select>

js：
data() {
    return {
    	classs:'',
		classsArr: [{name: "蓝色妖姬", table: "bluerose"}, {name: "烟叶",table: "tobaccoleaf"},{name: "佛手瓜",  table: "chayote"}]
    };
},
methods: {
	classSelect(e){
      	var table=''
		for (var i in this.classsArr) {
      		i=e.target.selectedIndex
			table=this.classsArr[i].table
		}
		console.log(table)
	},
}


或者
<select class="select select2" @change="classSelect"  v-model="classs">
	   <option v-for="item in classsArr" :key="item.table" v-bind:value="item.table" :label="item.name"></option>
</select>

js：
data() {
    return {
    	classs:'',
		classsArr: [{name: "蓝色妖姬", table: "bluerose"}, {name: "烟叶",table: "tobaccoleaf"},{name: "佛手瓜",  table: "chayote"}]
    };
},
methods: {
	classSelect(){
      	console.log(this.classs)
	},
}