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node.js - 函数在nodejs中没有返回任何东西

问题描述

我正在创建一个网络应用程序的后端，其中存储了不同的帖子并且还存储了它们的类别。由于每个类别都有自己的属性（如描述、颜色等），因此我创建了一个新的类别架构并将类别引用存储在文章中。这是我的发帖路线： Code_1
Code_2

// CREATE ROUTE : adding New Article
app.post("/addnew", upload.single('image'), function(req,res){

//get data from form and add to news array 
var title = req.body.title;
var image = req.body.image
if (req.file){
    var imgURL = req.file.path;
}

var description = req.body.description;
var category = req.body.category;
var tag = req.body.tag;


// Handling the category entered by user
function checkCategory(name , color, totalArticles, desc){Category.find({name: category}, (err, foundCategory) => {
    if(err){
        console.log(err)
    } else {
        console.log("found category in starting of checkCategory function : " , foundCategory)
        if (foundCategory[0]){
            console.log("Category" + foundCategory + "already exists...")
            return foundCategory
        } else {
            // var name = req.body.name
            // var color = req.body.color
            // var totalArticles = req.body.totalArticles
            // var desc  = req.body.desc
            var category = {name: name , color : color , totalArticles: totalArticles || 0 , desc : desc }
            Category.create(category, (err, newCategory) => {
                if (err){
                    console.log(err)
                } else {
                    console.log("New category Created : " , newCategory)
                    // category = newCategory
                    return newCategory
                }
                
            })
        }
    }
    })
}

console.log("??????????????? category returned", category)
var nyaArticle= {title: title, imgURL: imgURL, description: description};

// create a new Article and save to db 
Article.create(nyaArticle,function(err,newArticle){
    if(err){
        console.log(err);
    } else {
        // redirect back to main page
        console.log("new article created")
        console.log(newArticle)
        category = checkCategory(req.body.name, req.body.color, req.body.totalArticles, req.body.desc)
        console.log("checkCategory Returned :::::" , category)
        newArticle.category.push(category)
        newArticle.save() 
        res.redirect("/");
    }
})

函数 checkCategory 检查类别是否已经存在，否则它将创建一个新类别。但是根据这些日志，我的函数没有返回创建的类别，但是该类别已在 DB 中成功创建，也可以在Logs中看到

Articles App has started on port 3000
DB Connected...: cluster0-shard-00-00-ktzf1.mongodb.net
??????????????? category returned undefined
new article created
{
  category: [],
  hits: 0,
  tag: [],
  comments: [],
  _id: 60be0fe92a8b88a8fcea71dc,
  title: 'TESTING',
  description: 'TESTING',
  created: 2021-06-07T12:24:09.563Z,
  __v: 0
}
checkCategory Returned ::::: undefined
found category in starting of checkCategory function :  []
New category Created :  {
  totalArticles: 444,
  _id: 60be0fea2a8b88a8fcea71dd,
  name: 'TESTING',
  color: 'RED ALERT',
  desc: 'THiS TESTING',
  __v: 0
}

由于这个 null 被存储在我的 DB类别中

我是使用正确的方法还是应该遵循其他方法，非常欢迎任何帮助。

categorySchema 如下所示：

var categorySchema = new mongoose.Schema({ name: String, color: String, totalArticles: { type:Number, default: 0 }, desc : String });

文章架构：

var newSchema  = new mongoose.Schema({
title: String,
imgURL: String,                                            //{type: String, default: "https://source.unsplash.com/1600x1080/?news"},
description: String,
// category: String,
category: [
    {
        type: mongoose.Schema.Types.ObjectId,
        ref: "Category"
    }
],
hits : {
    type: Number , 
    default : 0 
},
tag: [
    {type: String}
],
created: {type: Date, default: Date.now},
comments: [
    {
        type: mongoose.Schema.Types.ObjectId,
        ref: "Comment"
    }
]

});

标签： node.jsmongodbexpressmongoose

解决方案

您正在从您的返回的回调函数var category内部进行分配，并且该 var 仅在该回调中可用。 此外，您的代码还有其他几个问题，例如永远不会返回任何内容。（应该是）。 一般来说，使用 , 会更好（如果你愿意，可以加上 a ）：checkCategory
Category.find({name: category}){name:name}
async\awaittry\catch

async function checkCategory(name, color, totalArticles, desc) {

    try {
        let category = await Category.findOne({ name });
        if (category) {
            console.log(`Category ${category.name} already exists...`);
            return category;
        }
        else {
            let newCategory = await Category.create({ name: name, color: color, totalArticles: totalArticles || 0, desc: desc });
            console.log("New category Created : ", newCategory);
            return newCategory;
        }
    } catch (error) {
        console.log(err)
    }
}

在您的路由器功能中：

app.post("/addnew", upload.single('image'), async function(req,res){

let {name, color, totalArticles, desc} = req.body;
let category = await checkCategory(name, color, totalArticles, desc);

let newArticle = await Article.create({ title: title, imgURL: imgURL, description: description, category: [category] });
res.redirect("/");
}

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