Javascript 正在尝试分析mongoose对象

因此，我正在调用mongodb，在解析数据以便将其传递给视图时遇到了问题。我用EJS编写前端

这就是我要呼叫的模型：

const CourseworkSchema = new Schema({
assignment: [
    {
        type: String
    }
],
author: {
    id: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User'
    },
    name: String
}
})

module.exports = mongoose.model('Coursework', CourseworkSchema);

以下是我称之为Corsework的路线：

app.get('/dashboard', (req, res) => {
if(req.isAuthenticated()){
    if(req.user.isTeacher) {
        // render dashboard for teacher
        //let author = author._id
        let arr = Coursework.find({  })
        //console.log(arr)
        let val = JSON.stringify(arr.assignment)
        //console.log(val)
        console.log(arr.assignment)
        res.render('instructor', {arr: val, isAuth:req.isAuthenticated()})
    }else {
        // render dashboard for student
        res.render('student', {isAuth: req.isAuthenticated()})
    }
}

我需要在视图中使用赋值。 每次我试图将其字符串化时，它都被认为是未定义的。 如何解析它，以便使用属性author和assignment

任何帮助都将不胜感激

请尝试以下代码：

app.get('/dashboard', async (req, res) => {
    if(req.isAuthenticated()){
        if(req.user.isTeacher) {
            // render dashboard for teacher
            //let author = author._id
            let arr = await Coursework.find({}).lean(true).exec();
            //console.log(arr)
            /** 
              * As `.find()` returns an array & to access `assignment` field on each doc, You need to iterate over.
              * let val = JSON.stringify(arr.assignment) has to be replaced
              */
            let val = arr.map((i)=> {return JSON.stringify(i.assignment)}) // will be an array of parsed `assignment` values
            //console.log(val)
            res.render('instructor', {arr: val, isAuth:req.isAuthenticated()})
        }else {
            // render dashboard for student
            res.render('student', {isAuth: req.isAuthenticated()})
        }
    }

由于Node.Js是异步的，所以它不会等到DB操作Coursework.find{}完成。因此，您需要等待DB find调用完成，然后arr将被填充数据，并且仅用于打印，我们不需要使用.lean，但如果您想更改/操作返回文档中的字段，则必须将mongoose文档转换为.Js对象以供进一步使用。此外，您需要在try-catch块中包装此代码，因为建议在try-catch中包装异步函数

注意：如果您正在使用author.\u id-对唯一字段进行筛选，那么请尝试使用.findOne，它将返回null或匹配的文档，这有助于我们避免在数组上进行不必要的迭代。

此行让arr=Coursework.find{}返回一个文档数组。您必须迭代arr以获得特定的赋值，而简单的arr.assignment将不起作用

e、 g

正如您在下面的代码片段中所看到的，我创建了两个课程项目，然后对它们进行迭代以将它们记录到控制台

const mongoose = require('mongoose');

run().catch(error => console.log(error.stack));

async function run() {
    await mongoose.connect('mongodb://localhost:27017/test', { useNewUrlParser: true });
    await mongoose.connection.dropDatabase();

    const CourseworkSchema = new mongoose.Schema({
    assignment: [
        {
            type: String
        }
    ],
    author: {
        id: {
            type: mongoose.Schema.Types.ObjectId,
            ref: 'User'
        },
        name: String
    }
    });

    const CourseWork = mongoose.model('Coursework', CourseworkSchema);

    await CourseWork.create({ assignment: "first assignment", author: { name: "first author" }});
    await CourseWork.create({ assignment: "Second assignment", author: { name: "second author" }});

    const docs = await CourseWork.find();
    console.log(docs);

    for (const doc of docs) {
        console.log(doc.assignment);
        console.log(doc.author);
    }
}

---

还是undefined@RockySingh：哦，糟糕，我忽略了&只检查了console.logarr，但没有检查let val=JSON.stringifyarr.assignment，更新了所有场景的答案。。

const mongoose = require('mongoose');

run().catch(error => console.log(error.stack));

async function run() {
    await mongoose.connect('mongodb://localhost:27017/test', { useNewUrlParser: true });
    await mongoose.connection.dropDatabase();

    const CourseworkSchema = new mongoose.Schema({
    assignment: [
        {
            type: String
        }
    ],
    author: {
        id: {
            type: mongoose.Schema.Types.ObjectId,
            ref: 'User'
        },
        name: String
    }
    });

    const CourseWork = mongoose.model('Coursework', CourseworkSchema);

    await CourseWork.create({ assignment: "first assignment", author: { name: "first author" }});
    await CourseWork.create({ assignment: "Second assignment", author: { name: "second author" }});

    const docs = await CourseWork.find();
    console.log(docs);

    for (const doc of docs) {
        console.log(doc.assignment);
        console.log(doc.author);
    }
}