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嘗試解析貓鼬對(duì)象

JavaScript

米琪卡哇伊 2022-08-27 09:48:37

所以我調(diào)用mongodb，我在解析數(shù)據(jù)時(shí)遇到問(wèn)題，因此我可以將其傳遞給視圖。我在EJS中編寫了前端。這就是我稱之為模型：const CourseworkSchema = new Schema({assignment: [ { type: String }],author: { id: { type: mongoose.Schema.Types.ObjectId, ref: 'User' }, name: String}})module.exports = mongoose.model('Coursework', CourseworkSchema);以下是我稱之為科西嘉會(huì)的路線：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()}) }}我需要在視圖中使用賦值。每次我試圖字符串化時(shí)，它都會(huì)顯示為.如何解析它，以便使用屬性和.undefinedauthorassigment任何幫助將不勝感激。

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2 回答

交互式愛情

TA貢獻(xiàn)1712條經(jīng)驗(yàn) 獲得超3個(gè)贊

此行返回一個(gè)文檔數(shù)組。您必須迭代才能獲得特定的賦值，而簡(jiǎn)單操作將不起作用let arr = Coursework.find({ })arrarr.assignment

例如

let arr = await Coursework.find({ })

for (const doc of arr) {

console.log(doc.assignment);

console.log(doc.author);

}

正如您在以下代碼片段中看到的那樣，我創(chuàng)建了兩個(gè)CourseWork項(xiàng)目，然后迭代它們以將它們記錄到控制臺(tái)

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);

}

反對(duì) 回復(fù) 2022-08-27

梵蒂岡之花

TA貢獻(xiàn)1900條經(jīng)驗(yàn) 獲得超5個(gè)贊

試試下面的代碼：

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是異步的，它不會(huì)等到DB操作完成。因此，您需要等到DB find調(diào)用完成，然后將填充數(shù)據(jù)，并且對(duì)于打印，我們不需要使用，但是如果您想更改/操作返回文檔中的字段，那么您必須將貓鼬文檔轉(zhuǎn)換為。供進(jìn)一步使用的 Js 對(duì)象。此外，您需要將此代碼包裝在塊中，因?yàn)榻ㄗh將函數(shù)包裝在try catch中。Coursework.find({})arr.lean()try-catchasync

注意：如果您正在檢查對(duì)唯一字段的 using - 類型的篩選，請(qǐng)嘗試使用將返回其中一個(gè)或匹配的文檔，這有助于我們避免對(duì)數(shù)組進(jìn)行不必要的迭代。authorauthor._id.findOne()null

反對(duì) 回復(fù) 2022-08-27