如果react js中的自动完成组合框中没有选中任何值，如何发出警报？

import React, { useState } from 'react';

const Autocomplete = () => {
  const [selectedValue, setSelectedValue] = useState('');

  const handleValueChange = (event) => {
    setSelectedValue(event.target.value);
  };

  const handleSubmit = (event) => {
    event.preventDefault();

    if (selectedValue === '') {
      alert('请先选择一个值！');
    } else {
      // 处理选中的值
    }
  };

  return (
    <form onSubmit={handleSubmit}>
      <input
        type="text"
        value={selectedValue}
        onChange={handleValueChange}
        placeholder="请输入值"
      />
      <button type="submit">提交</button>
    </form>
  );
};

export default Autocomplete;