如何在表单或OR中验证单选按钮域？

<form id="myForm">
  <label>
    <input type="radio" name="gender" value="male"> Male
  </label>
  <label>
    <input type="radio" name="gender" value="female"> Female
  </label>
  <button type="submit">Submit</button>
</form>

document.getElementById('myForm').addEventListener('submit', function(event) {
  const genderRadios = document.getElementsByName('gender');
  let isChecked = false;
  for (let i = 0; i < genderRadios.length; i++) {
    if (genderRadios[i].checked) {
      isChecked = true;
      break;
    }
  }
  if (!isChecked) {
    alert('Please select your gender.');
    event.preventDefault();
  }
});

const express = require('express');
const app = express();

app.use(express.urlencoded({ extended: true }));

app.post('/submit', (req, res) => {
  if (!req.body.gender) {
    return res.status(400).send('Gender is required.');
  }
  // Proceed with further processing
  res.send('Form submitted successfully.');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

const { Model, DataTypes } = require('sequelize');
const sequelize = new Sequelize('sqlite::memory:');

class User extends Model {}
User.init({
  gender: {
    type: DataTypes.ENUM('male', 'female'),
    allowNull: false,
    validate: {
      notNull: { msg: 'Gender is required.' },
      notEmpty: { msg: 'Gender cannot be empty.' }
    }
  }
}, { sequelize, modelName: 'user' });

(async () => {
  await sequelize.sync({ force: true });
  try {
    await User.create({ gender: null }); // This will fail due to validation
  } catch (error) {
    console.error(error.message); // Output: Gender is required.
  }
})();