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ERROR: TypeError: Cannot read properties of undefined (reading 'username')(错误：TypeError：无法读取未定义的属性(正在读取‘UserName’))

转载 作者：bug小助手 更新时间：2023-10-24 23:18:11 30 4
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This is my whole code. I am trying to locate on my page.ejs page through /insta/:id but it is showing the error:

这是我的全部代码。我试图通过/insta/：id在我的page.ejs页面上查找，但它显示错误：


Cannot read properties of undefined (reading 'username').

无法读取未定义的属性(正在读取‘UserName’)。


I want to get id that uuidv4() will be giving but instead it is returning username. And also I want to get the specific post through the id(which is getting username value and not the generated id) but my post variable didn't get any specific post in it.

我希望获得uuidv4()将提供的id，但它返回的是用户名。我还想通过id(它获取的是用户名值，而不是生成的id)来获取特定的帖子，但我的post变量没有在其中获取任何特定的帖子。


This is index.js


const express=require("express");
const app=express();
const path=require("path");
const { v4: uuidv4 } = require('uuid');
const port=3000;

let posts=[
    {   
        username:"evablue@2",
        image:"/post1.jpg",
        content:"Enjoying at this beautiful beach :)",
        tags:"",
        id:uuidv4(),
    },
    {
        username:"purple_whale",
        image:"/post2.jpg",
        content:"A pic should be clicked before digging in <**>",
        tags:"@shresDrawMystry, @riddhiMolala",
        id:uuidv4(),
    },
    {
        username:"nature'sBaby",
        image:"/post3.avif",
        content:"Love clicking beautiful moments.",
        tags:"@bankpyt",
        id:uuidv4(),
    },
    {
        username:"butterscoth#Love",
        image:"/post4.jpg",
        content:"It's Holi.Woooooohoooo.",
        tags:"",
        id:uuidv4(),
    },
    {
        username:"coffeeLover",
        image:"/post5.jpg",
        content:"Explored a new Cafe.",
        tags:"@RelaxCafe",
        id:uuidv4(),
    }
]

app.use(express.urlencoded({ extended:true }))
app.use(express.json());
app.use(express.static("public"));

app.set("view engine","ejs");
app.set("views",path.join(__dirname,"/views"));

app.get("/insta",(req,res)=>{
    res.render("home.ejs",{ posts });
})
app.get("/insta/:id",(req,res)=>{     
    let {id}=req.params;
    let post=posts.find((p)=> id===p.id );
    console.log(req.params);
    res.render("page.ejs",{ post });
})


app.listen(port,()=>{
    console.log("Port 3000 is listening requests");
})

This is page.ejs


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="https://fonts.googleapis.com/css2?        family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@24,400,0,0" />
    <title><%= post.username %></title>
</head>
<body>
    <div class="header">
        <div class="dp">
            <img src="<%= post.image %>">
        </div>
        <div class="info">
            <h5><%= post.username %></h5>
            <button>Follow</button>
            <button>Message</button>
             <button><span class="material-symbols-outlined">person_add</span></button>
        </div>
    </div>
</body>
</html>

更多回答
优秀答案推荐

You are getting the error: Cannot read properties of undefined (reading 'username') from your page.ejs file when you try to access username here:

出现错误：当您尝试访问此处的用户名时，无法从您的Page.ejs文件中读取未定义的属性(正在读取‘Username’)：


<title><%= post.username %></title>

The post object is empty because of the way you are using the uuid library.

由于您使用UUID库的方式，POST对象为空。


When you create your posts array, the uuidv4() function generates a new value every time your server restarts:

创建POSTS数组时，uuidv4()函数会在服务器每次重新启动时生成一个新值：


let posts=[
    {   
        username:"evablue@2",
        image:"/post1.jpg",
        content:"Enjoying at this beautiful beach :)",
        tags:"",
        id:uuidv4(), // id:2d98e533-769e-4352-83ea-c4fdbc516d73
    },
    {
        username:"purple_whale",
        image:"/post2.jpg",
        content:"A pic should be clicked before digging in <**>",
        tags:"@shresDrawMystry, @riddhiMolala",
        id:uuidv4(), // id:6064012d-cf4f-4445-88c8-e62d25153c98
    },
    ...
];

How do you know which value to pass to your app.get("/insta/:id" route?

如何知道将哪个值传递给app.get(“/insta/：id”路由？


Your router looks fine but you would need to add console.log('posts:', posts) straight after you create the array so you can actually see what value the uuidv4() has added for each id within the posts array. You could then navigate to:

您的路由器看起来很好，但是您需要在创建数组之后立即添加console.log(‘post：’，post)，这样您就可以实际看到uuidv4()为post数组中的每个id添加了什么值。然后，您可以导航到：


'http://localhaost:3000/insta/6064012d-cf4f-4445-88c8-e62d25153c98'
                            //^^ Replace this with one of the values shown in the console.log('posts:', posts)

However, this is very cumbersome and you should just use a database like MySQL or MongoDB. I appreciate that will be another technical challenge but you won't be able to rely on an array forever. Read the docs and have faith in yourself!

然而，这非常麻烦，您应该只使用MySQL或MongoDB这样的数据库。我知道这将是另一个技术挑战，但您不能永远依赖数组。阅读文档，对自己有信心！


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