如何使用mongoose获取文档的特定键值

npm install mongoose

const mongoose = require('mongoose');

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

const Schema = mongoose.Schema;

const mySchema = new Schema({
  key1: String,
  key2: Number,
  key3: Boolean
});

const MyModel = mongoose.model('MyModel', mySchema);

MyModel.findOne({ key1: 'value1' })
  .then((document) => {
    if (document) {
      const specificValue = document.key2;
      console.log('Specific value:', specificValue);
    } else {
      console.log('Document not found');
    }
  })
  .catch((error) => {
    console.error('Error retrieving document:', error);
  });