从Node js / MongoDB中的另一个文档向对象注入值

Question

我正在开发一个基于React（前端）和Node js（后端为 mongodb ）的应用程序。在同事处理后端时，我主要是在前端上工作。该应用程序的数据库结构如下：
当我在数据库中添加问题时，我提供了一个选项列表，其中一个是答案。在后端，问题存储在单独的文档中，而答案存储在单独的文档中；持有问题的ID作为参考。问题文档的外观为。另一方面，答案文档的结构为。如您所见，每个答案对象都持有对其各自问题的引用。如果我发出HTTP GET请求以获取问题列表，它将返回带有空答案数组的问题对象。但是，这不是所需的行为。后端代码段如下：

const _ = require('lodash');
const {Question, validate} = require('../models/questions');
const {Answer} = require('../models/answers');
const mongoose = require('mongoose');
const express = require('express');
const router = express.Router();

router.get('/', async (req, res) => {
  const questions = await Question.find({ isDeleted: false }).sort('dateCreated');
  res.send(questions);
});

router.post('/', async (req, res) => {
  const { error } = validate(req.body); 
  if (error) return res.status(400).send(error.details[0].message);

  let question = new Question(_.pick(req.body, ['questionText', 'sectionId']));

  //save data in collection
  await question.save();

  let ans_Obj= req.body.answer;
  Object.keys(ans_Obj).map( async function(key) {
    let answer = new Answer({
        ans_text: ans_Obj[key].answer,
        questionId: question._id,
        isCorrect: ans_Obj[key].isCorrect
    });

    /// save answers for given question ID
    await answer.save();
  });

  res.send(question);
});

router.put('/:id', async (req, res) => {
  const { error } = validate(req.body); 
  if (error) return res.status(400).send(error.details[0].message);

  const question = await Question.findByIdAndUpdate(req.params.id, 
    { 
      questionText: req.body.questionText,
      sectionId: req.body.sectionId,
      dateModified: new Date()
    }, {
    new: true
  });

  /// need to update ans as well, if admin removes or updates any ans.
  ///left it for future implementation



  if (!question) return res.status(404).send('The question with the given ID was not found.');

  res.send(question);
});

router.delete('/:id', async (req, res) => {
  const question = await Question.findByIdAndUpdate(req.params.id, 
    { 
      isDeleted:true
    },{
      new:true
    });

  if (!question) return res.status(404).send('The question with the given ID was not found..');

  res.send(question);
});

router.get('/:id', async (req, res) => {
  const question = await Question.findById(req.params.id);

  if (!question) return res.status(404).send('The question with the given ID was not found.');

  res.send(question);
});

module.exports = router;

如您所见，在router.GET部分中，仅会提取问题，因为它会返回空答案数组。 我的问题是：如何从ANSWERS文档中检索答案并将答案插入各自的问题中？如有任何帮助或建议，请先感谢。