el-select数据过多懒加载的解决(loadmore)

<template>
 <el-select
 v-model="value"
 placeholder="请选择"
 filterable
 multiple
 v-el-select-loadmore="loadmore"
 >
 <el-option
 v-for="item in options"
 :key="item.id"
 :label="item.label"
 :value="item.id">
 </el-option>
 </el-select>
</template>
 
export default {
 directives: {
 'el-select-loadmore': {
 bind(el, binding) {
 // 获取element-ui定义好的scroll盒子
 const SELECTWRAP_DOM = el.querySelector('.el-select-dropdown .el-select-dropdown__wrap');
 SELECTWRAP_DOM.addEventListener('scroll', function () {
 /**
 * scrollHeight 获取元素内容高度(只读)
 * scrollTop 获取或者设置元素的偏移值,常用于, 计算滚动条的位置, 当一个元素的容器没有产生垂直方向的滚动条, 那它的scrollTop的值默认为0.
 * clientHeight 读取元素的可见高度(只读)
 * 如果元素滚动到底, 下面等式返回true, 没有则返回false:
 * ele.scrollHeight - ele.scrollTop === ele.clientHeight;
 */
 const condition = this.scrollHeight - this.scrollTop <= this.clientHeight;
 if (condition) {
 binding.value();
 }
 });
 }
 }
 },
 data() {
 return {
 value: '',
 options: [],
 formData: {
 pageIndex: 1,
 pageSize: 20,
 }
 };
 },
 mounted() {
 this.getList(this.formData);
 },
 methods: {
 loadmore() {
 this.formData.pageIndex++;
 this.getList(this.formData);
 },
 getList(formData) {
 // 这里是接口请求数据, 带分页条件
 const _res = [1, 2, 3]; // 请求得到的数据
 this.options = [...this.options, ..._res];
 }
 }
};