在mongoose中使用populate

const mongoose = require('mongoose');

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

const articleSchema = new mongoose.Schema({
  title: String,
  content: String,
  author: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User' // 关联到User集合
  }
});

const User = mongoose.model('User', userSchema);
const Article = mongoose.model('Article', articleSchema);

Article.find().populate('author').exec((err, articles) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(articles);
});

Article.find().populate({ path: 'author', select: 'name' }).exec((err, articles) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(articles);
});

Article.find().populate('author department').exec((err, articles) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(articles);
});