删除父级时，Mongoose删除子文档引用

const mongoose = require('mongoose');

// 子文档模式
const childSchema = new mongoose.Schema({
  name: String
});

// 父级文档模式
const parentSchema = new mongoose.Schema({
  name: String,
  children: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Child' }]
});

const Child = mongoose.model('Child', childSchema);
const Parent = mongoose.model('Parent', parentSchema);

parentSchema.pre('remove', function(next) {
  // 删除子文档引用
  Child.remove({ _id: { $in: this.children } })
    .then(() => next())
    .catch(err => next(err));
});

Parent.findById(parentId)
  .then(parent => {
    if (!parent) {
      throw new Error('父级文档不存在');
    }
    // 删除父级文档
    return parent.remove();
  })
  .then(() => {
    console.log('父级文档及其子文档引用删除成功');
  })
  .catch(err => {
    console.error(err);
  });