如何在mongoose查询中连接多个字段？

const mongoose = require('mongoose');

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

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

// 连接数据库
mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => {
    console.log('Connected to database');
    
    // 查询条件
    const query = {
      $and: [
        { name: 'John' },
        { age: { $gte: 18 } },
        { email: { $regex: /gmail\.com$/i } }
      ]
    };
    
    // 执行查询
    User.find(query)
      .then(users => {
        console.log(users);
      })
      .catch(error => {
        console.error(error);
      });
  })
  .catch(error => {
    console.error('Failed to connect to database', error);
  });