mongoose救命，为什么我变空了？

const User = mongoose.model('User', userSchema);

// 错误的查询条件
const user = await User.findOne({ name: 'NonExistentUser' });
console.log(user); // 输出: null

// 正确的查询条件
const user = await User.findOne({ name: 'ExistingUser' });
console.log(user); // 输出: { _id: ..., name: 'ExistingUser', ... }

mongoose.connect('mongodb://localhost:27017/mydatabase', {
  useNewUrlParser: true,
  useUnifiedTopology: true,
}).then(() => {
  console.log('Connected to MongoDB');
}).catch((err) => {
  console.error('Connection error:', err);
});

const newUser = new User({
  name: 'John Doe',
  email: 'john.doe@example.com'
});

newUser.save().then((savedUser) => {
  console.log(savedUser); // 输出: { _id: ..., name: 'John Doe', email: 'john.doe@example.com', ... }
}).catch((err) => {
  console.error('Save error:', err);
});

User.findByIdAndUpdate(
  'existingUserId',
  { name: '' }, // 这里将名字更新为空字符串
  { new: true }
).then((updatedUser) => {
  console.log(updatedUser); // 输出: { _id: ..., name: '', email: '...', ... }
}).catch((err) => {
  console.error('Update error:', err);
});

const user = await User.findOne({ name: 'ExistingUser' });
if (user) {
  console.log('User found:', user);
} else {
  console.log('User not found');
}

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/mydatabase', {
  useNewUrlParser: true,
  useUnifiedTopology: true,
}).then(() => {
  console.log('Connected to MongoDB');
}).catch((err) => {
  console.error('Connection error:', err);
});

const userSchema = new mongoose.Schema({
  name: String,
  email: String
});

const User = mongoose.model('User', userSchema);

// 保存文档
const newUser = new User({
  name: 'John Doe',
  email: 'john.doe@example.com'
});

newUser.save().then((savedUser) => {
  console.log('Saved user:', savedUser);

  // 更新文档
  return User.findByIdAndUpdate(savedUser._id, { name: 'Jane Doe' }, { new: true });
}).then((updatedUser) => {
  console.log('Updated user:', updatedUser);

  // 查询文档
  return User.findOne({ name: 'Jane Doe' });
}).then((foundUser) => {
  console.log('Found user:', foundUser);
}).catch((err) => {
  console.error('Error:', err);
});