如何在不检索文档的情况下检查文档是否存在: Mongoose

const mongoose = require('mongoose');

// 连接到MongoDB数据库
mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => {
    console.log('Connected to MongoDB');
  })
  .catch((error) => {
    console.error('Failed to connect to MongoDB', error);
  });

// 定义文档模型
const User = mongoose.model('User', new mongoose.Schema({
  name: String,
  age: Number
}));

// 检查文档是否存在
User.exists({ name: 'John' })
  .then((exists) => {
    if (exists) {
      console.log('Document exists');
    } else {
      console.log('Document does not exist');
    }
  })
  .catch((error) => {
    console.error('Failed to check document existence', error);
  });