我在快递js中将html转换为pug时遇到错误

我是node.js的新手 . 我收到了这个错误

TypeError：/home/agile/projects/nodekb/views/index.pug:6 4 | h1＃ 5 | ul> 6 |每篇文章，我在文章7 | li = article.title无法读取eval中未定义的属性“length”（包装时的eval（/home/agile/projects/nodekb/node_modules/pug-runtime/wrap.js:6:10）,:28：32）at eval（eval at wrap（/home/agile/projects/nodekb/node_modules/pug-runtime/wrap.js:6:10），：47：4）at template（eval at wrap（/ home / agile / projects / nodekb） /node_modules/pug-runtime/wrap.js:6:10），：58：136）at Object.exports.renderFile（/home/agile/projects/nodekb/node_modules/pug/lib/index.js:427:38 ）在View.exports .__ express [作为引擎]的Object.exports.renderFile（/home/agile/projects/nodekb/node_modules/pug/lib/index.js:417:21）中（/ home / agile / projects / nodekb） /node_modules/pug/lib/index.js:464:11）在try.render（/home/agile/projects/nodekb/node_modules/express/lib/view.js:135:8）的tryRender（/ home / agile） /projects/nodekb/node_modules/express/lib/application.js:640:10）在ServerResponse的Function.render（/home/agile/projects/nodekb/node_modules/express/lib/application.js:592:3） . 渲染（/ home / agile / projects / nodekb / node_modules / expre SS / LIB / response.js：1008：7）

这是我的代码，views / index.pug

extends layout

block content
  h1 #{title}
  ul
    each article, i in articles
      li= article.title

app.js

const express = require('express');
const path = require('path');

//init app
const app = express();

//load  view engine
app.set('views', path.join(__dirname, 'views'));
app.set('view engine','pug');

//home route
app.get('/', function(req,res){
    let articles =[
        {
            id:1,
            title: 'Article 1',
            author: 'Bhakti Thakkar',
            body: 'This is article one'
        },
        {
            id:2,
            title: 'Article 2',
            author: 'Jeel Thakkar',
            body: 'This is article two'
        },
        {
            id:1,
            title: 'Article 3',
            author: 'Sonal Thakkar',
            body: 'This is article three'
        }
    ];
    res.render('index',{
        title:'Articles'
    });
});


//add route
app.get("/articles/add",function(req,res){
    res.render('add_article',{
        title:'Add Articles'
    })
});

//start server
app.listen(3000, function(){
    console.log('Server started on port 3000...');
});

意见/ layout.pug

doctype html
html
    head
        title Knowledgebase
    body   
        block content
        br
        hr
        footer
            p Copyright © 2018