src/utils/loadmore.js

export default {
  bind(el, binding) {
    const selectDom = el.querySelector('.el-select-dropdown .el-select-dropdown__wrap')
    selectDom.addEventListener('scroll', () => {
      if (selectDom.scrollHeight - selectDom.scrollTop <= selectDom.clientHeight + 20) {
        binding.value()
      }
    })
  }
};