如何在mongoose中获取populate()中的值？

const mongoose = require('mongoose');

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

const bookSchema = new mongoose.Schema({
  title: String,
  author: { type: mongoose.Schema.Types.ObjectId, ref: 'Author' },
});

const Author = mongoose.model('Author', authorSchema);
const Book = mongoose.model('Book', bookSchema);

Book.find()
  .populate('author') // 这里填充author字段
  .exec((err, books) => {
    if (err) return handleError(err);

    // 现在每个book对象的author字段已经被替换为对应的Author文档
    console.log(books[0].author.name); // 输出作者的名字
  });

Book.find()
  .populate('author')
  .exec((err, books) => {
    if (err) {
      console.error('Error populating data:', err);
      return;
    }
    // 正确处理数据
    console.log(books);
  });