为什么缺少一个字段？

const express = require('express');
const app = express();
app.use(express.json());

app.post('/users', (req, res) => {
  const { name, age } = req.body;
  // 检查是否缺少email字段
  if (!req.body.email) {
    return res.status(400).json({ error: 'Missing email field' });
  }
  // 处理用户创建逻辑
  res.status(201).json({ message: 'User created successfully', user: { name, age, email: req.body.email } });
});

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

fetch('/users', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    name: 'John Doe',
    age: 30,
    email: 'john.doe@example.com' // 确保包含所有必要的字段
  })
})
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));