子文档的Mongoose中的findById

const mongoose = require('mongoose');

// 定义子文档的Schema
const commentSchema = new mongoose.Schema({
  content: String,
  author: String
});

// 定义父文档的Schema
const blogPostSchema = new mongoose.Schema({
  title: String,
  content: String,
  comments: [commentSchema] // 嵌套子文档
});

// 定义父文档的Model
const BlogPost = mongoose.model('BlogPost', blogPostSchema);

// 查找子文档
BlogPost.findById(subdocumentId)
  .then((subdocument) => {
    // 处理查询结果
    console.log(subdocument);
  })
  .catch((error) => {
    // 处理错误
    console.error(error);
  });