您需要填充已回答的字段。

const = questions = await Question.find().populate('answered');

您需要这样填充：（这也是排除用户密码的好主意）

 Question.find({})
    .populate("user","-password")
    .populate("answered.user","-password");

我还有一些代码建议：

我们通常在模型（例如User）中使用首字母大写和单数名称。

user.js

const mongoose = require("mongoose");

const UserSchema = new mongoose.Schema({
  name: {
    type: String,required: true
  },email: {
    type: String,required: true,unique: true
  },password: {
    type: String,date: {
    type: Date,default: Date.now
  }
});

const User = mongoose.model("User",UserSchema);

module.exports = User;

question.js

const mongoose = require("mongoose");

const QuestionSchema = new mongoose.Schema({
  user: {
    type: mongoose.Schema.Types.ObjectId,ref: "User"
  },question: {
    type: String
  },name: {
    type: String
  },answered: [
    {
      user: {
        type: mongoose.Schema.Types.ObjectId,ref: "User"
      }
    }
  ]
});

const Question = mongoose.model("Question",QuestionSchema);

module.exports = Question;

您可以使用以下查询填充用户：

const Question = require("../models/question");

router.get("/question",async (req,res) => {
  const questions = await Question.find({})
    .populate("user","-password");

  res.send(questions);
});

以下是示例输出：

[
    {
        "_id": "5dc12a6aa875cd0ca8b871eb","user": {
            "_id": "5dc129eda875cd0ca8b871e8","name": "user 1","email": "user1@gmail.com","date": "2019-11-05T07:51:09.625Z","__v": 0
        },"question": "question 1","name": "question 1 name","answered": [
            {
                "_id": "5dc12a6aa875cd0ca8b871ed","user": {
                    "_id": "5dc12a00a875cd0ca8b871e9","name": "user 2","email": "user2@gmail.com","date": "2019-11-05T07:51:28.892Z","__v": 0
                }
            },{
                "_id": "5dc12a6aa875cd0ca8b871ec","user": {
                    "_id": "5dc12a0aa875cd0ca8b871ea","name": "user 3","email": "user3@gmail.com","date": "2019-11-05T07:51:38.060Z","__v": 0
                }
            }
        ],"__v": 0
    }
]