very basic web application error in express

Question

hello this is my first post. I'm a beginner of coding, so i watching video of opentutorials.org/course/2136/11950

i tried to find error in my code. but i can't not TT

When we enter site, it shows data lists. [localhost:3000/topic] enter image description here

and click the list, it shows description. like this. enter image description here

but in my case.. every text makes li... how can i do? enter image description here

//app.js
const express = require('express'); //가져오기
const bodyParser = require('body-parser');//가져오기
const fs = require('fs');
const { title } = require('process');
const app = express();
app.use(bodyParser.urlencoded({extended:false})); //bodyParser를 사용하겠다.
app.locals.pretty = true;
app.set('views', './views') //템플릿엔진 위치 설정
app.set('view engine', 'pug')//어떤 엔진사용할건지 설정
app.get('/topic/new', (req, res) =>  res.render('new') );
app.get('/topic', (req, res) => {
    fs.readdir('data',(err, data) => {
        if(err){//에러가 있다면
            res.status(500).send('Internal Server Error');
        }
        res.render('view', {topics : data}); //사용자가 topic에들어오면 글목록보이기
    })
    } );
    
app.get('/topic/:id',(req, res)=>{
    const id = req.params.id;
    fs.readdir('data',(err, data)=>{
        if(err){
            res.status(500).send('Internal Server Error');
        }
    })
        fs.readFile('data/'+id, 'utf8', (err, data) =>{
            if(err){//에러가 있다면
                res.status(500).send('Internal Server Error');
            }
           res.render('view',{title:id, topics : data, description:data });
        
        })
    })
    
 //바뀌는정보를 콜론+변수명
app.post('/topic',(req, res) => 
   {
    const title = req.body.title; 
    const description = req.body.description;
    //파일을 쓰게하기
    fs.writeFile('data/'+title, description,(err)=> { //data폴더에 title로 파일명, 내용은 description
        if(err){//에러가 있다면
            res.status(500).send('Internal Server Error');
        }
        res.send('Success!')
    });
   });



app.listen(3000, () => { console.log('connected 3000 port!')}) //port, 콜백(서버연결시 출력)

//view.pug
doctype html
html(lang="en")
    head
        meta(charset="UTF-8")
        meta(http-equiv="X-UA-Compatible", content="IE=edge")
        meta(name="viewport", content="width=device-width, initial-scale=1.0")
        title Document
    body
      h1 Server Side JavaScript 
      ul 
        each topic in topics
          li 
            a(href="/topic/"+topic)= topic
    article 
       h2= title

Answer 1

The render variable in app.get('/topic/:id') is incorrectly set. The below changes should render your view properly

app.get('/topic/:id',(req, res)=>{
    const id = req.params.id;
    let filesList = null
    fs.readdir('data',(err, data)=>{
        if(err){
            res.status(500).send('Internal Server Error');
        }
        // This variable should be returned for topics
        filesList = data
    })
        fs.readFile('data/'+id, 'utf8', (err, data) =>{
            if(err){//??? ???
                res.status(500).send('Internal Server Error');
            }
           // Update the topics variable
           res.render('view',{title:id, topics : filesList, description:data });
        
        })
    })