哈巴狗导航列表不起作用

Question

我正在关注YouTube上的一个教程，该教程告诉我制作侧面导航列表，并且在我遵循它时，出现了一个我不知道如何解决的错误。

简而言之，错误显示为：

  

37 | h3 = sideNavigationList [landingPage] .title   无法正确读取未定义的“标题”。

这是我名为“ nav.pug”的文件的代码：

-
    var sideNavigationList = {
        'Home': {
            title: 'HTML and CSS',
            linkList: [
                {label: 'Learn HTML', link: '/html'},
                {label: 'Learn CSS', link: '/css'},
                {label: 'Learn JavaScript', link: '/javascript'},
            ]
        },
        'HTML': {
            title: 'HTML Tutorial',
            linkList: [
                {label: 'HTML Elements', link: '/html/elements'},
                {label: 'HTML Attributes', link: '/html/attributes'},
                {label: 'HTML Headings', link: '/html/headings'},
            ]
        },
        'CSS': {
            title: 'CSS Tutorial',
            linkList: [
                {label: 'CSS Colors', link: '/css/colors'},
                {label: 'CSS Backgrounds', link: '/css/backgrounds'},
                {label: 'CSS Borders', link: '/css/borders'},
            ]
        },
        'JavaScript': {
            title: 'JavaScript Tutorial',
            linkList: [
                {label: 'JavaScript Comments', link: '/javascript/comments'},
                {label: 'JavaScript Variables', link: '/javascript/variables'},
                {label: 'JavaScript Operators', link: '/javascript/operators'},
            ]
        },
    }
nav 
    h3=sideNavigationList[landingPage].title
    each navigation in sideNavigationList[landingPage].linkList
        a(href=navigation.link)=navigation.label
        //- a(href="/html") Learn HTML
        //- a(href="/css") Learn CSS
        //- a(href="/javascript") Learn JavaScript

有人可以告诉我哪里出了问题以及如何解决？非常感谢你。 ：）