它确实添加了一个部分，但它不更新导航栏

Question

当我按下按钮添加一个部分时，它会添加一个部分，但不会更新导航栏它应该动态更新中殿栏，导航栏只显示已经存在的部分而不是我用 js 添加的部分我似乎没有注意到我做错了什么如果你有解决方案请继续

let sections = document.querySelectorAll("section");
let navList = document.getElementById("navbar__list");
const buildSecBtn = document.getElementById("newSection");
const main = document.querySelector("main");

/**
 * End Global Variables
 * Start Helper Functions
 * 
*/
let counter = 3;
const buildSection = () => {
    counter++
    const newSec =  ` <section id="section${counter}" data-nav="Section ${counter}">
        <div class="landing__container">
        <h2>Section ${counter}</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi fermentum metus faucibus lectus pharetra dapibus. Suspendisse potenti. Aenean aliquam elementum mi, ac euismod augue. Donec eget lacinia ex. Phasellus imperdiet porta orci eget mollis. Sed convallis sollicitudin mauris ac tincidunt. Donec bibendum, nulla eget bibendum consectetur, sem nisi aliquam leo, ut pulvinar quam nunc eu augue. Pellentesque maximus imperdiet elit a pharetra. Duis lectus mi, aliquam in mi quis, aliquam porttitor lacus. Morbi a tincidunt felis. Sed leo nunc, pharetra et elementum non, faucibus vitae elit. Integer nec libero venenatis libero ultricies molestie semper in tellus. Sed congue et odio sed euismod.</p>
        <p>Aliquam a convallis justo. Vivamus venenatis, erat eget pulvinar gravida, ipsum lacus aliquet velit, vel luctus diam ipsum a diam. Cras eu tincidunt arcu, vitae rhoncus purus. Vestibulum fermentum consectetur porttitor. Suspendisse imperdiet porttitor tortor, eget elementum tortor mollis non.</p>
        </div>
        </section>`
    main.insertAdjacentHTML("beforeend", newSec);

};



const buildNav = () => {
    navList.innerHTML ="";
    sections.forEach(section => { 
        const navItem = `<li><a class="menu__link" data-nav="${section.id}" href="${section.id}">${section.dataset.nav}</a></li>`
        navList.insertAdjacentHTML("beforeend",navItem)
    })
}
buildNav();

buildSecBtn.addEventListener("click", () => {
    buildSection();
    buildNav();
})

body {
    background: rgb(136,203,171);
    background: linear-gradient(0deg, rgba(136,203,171,1) 0%, rgba(0,13,60,1) 100%);
    margin: 0;
    font-family: 'Merriweather', serif;
    color: #fff;
}


/* Typeography General*/
h1 {
    font-family: 'Fira Sans', sans-serif;
    font-size: 3em;
    margin: 2em 1rem;
}

@media only screen and (min-width: 35em){
    h1 {
        font-size: 7em;
        margin: 2em 4rem 1em;
    }
}

h2 {
    border-bottom: 1px solid #cc1;
    font-family: 'Oxygen', Sans-Serif;
    font-size: 3em;
    color: #fff;
}

p {
    line-height: 1.6em;
    color: #eee;
}

/* ---- Layout Rules ---- */
main {
    margin: 10vh 1em 10vh;
}

.main-hero {
    min-height: 40vh;
    padding-top: 3em;
}

section {
    position: relative;
    min-height: 80vh;
}



.navbar__menu ul {
    padding-left: 0;
    margin: 0;
    text-align: right;
}

.navbar__menu li {
    display: inline-block;
}

.navbar__menu .menu__link {
    display: block;
    padding: 1em;
    font-weight: bold;
    text-decoration: none;
    color: #000;
}

.navbar__menu .menu__link:hover {
    background: #333;
    color: #fff;
    transition: ease 0.3s all;
}

/* Header Styles */
.page__header {
    background: #fff;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 5;
}

#newSection {
    background-color: black;
    position: sticky;
    width: 5rem;
    color: wheat;
}


.page__footer {
    background: #000;
    padding: 3em;
    color: #fff;
}

.page__footer p{
    color: #fff;
}


/* ---- Theme Rules ---- */
/* Landing Container Styles */
.landing__container {
    padding: 1em;
    text-align: left;
}

@media only screen and (min-width: 35em){
    .landing__container {
        max-width: 50em;
        padding: 4em;
    }
}

section:nth-of-type(even) .landing__container {
    margin-right: 0;
    margin-left: auto;
    text-align: right; 
}


section:nth-of-type(odd) .landing__container::before {
    content: '';
    background: rgba(255, 255, 255, 0.187);
    position: absolute;
    z-index: -5;
    width: 20vh;
    height: 20vh;
    border-radius: 50%;
    opacity: 0;
    transition: ease 0.5s all;
}

section:nth-of-type(even) .landing__container::before {
    content: '';
    background: rgb(255,255,255);
    background: linear-gradient(0deg, rgba(255,255,255,.1) 0%, rgba(255,255,255,.2) 100%);
    position: absolute;
    top: 3em;
    right: 3em;
    z-index: -5;
    width: 10vh;
    height: 10vh;
    border-radius: 50%;
    opacity: 0;
    transition: ease 0.5s all;
}

section:nth-of-type(3n) .landing__container::after {
    content: '';
    background: rgb(255,255,255);
    background: linear-gradient(0deg, rgba(255,255,255,.1) 0%, rgba(255,255,255,.2) 100%);
    position: absolute;
    right: 0;
    bottom: 0;
    z-index: -5;
    width: 10vh;
    height: 10vh;
    border-radius: 50%;
    opacity: 0;
    transition: ease 0.5s all;
}

section:nth-of-type(3n + 1) .landing__container::after {
    content: '';
    background: rgb(255,255,255);
    background: linear-gradient(0deg, rgba(255,255,255,.1) 0%, rgba(255,255,255,.2) 100%);
    position: absolute;
    right: 20vw;
    bottom: -5em;
    z-index: -5;
    width: 15vh;
    height: 15vh;
    border-radius: 50%;
    opacity: 0;
    transition: ease 0.5s all;
}



section.your-active-class {
    background: rgb(0, 0, 0);
    background: linear-gradient(0deg, rgba(0, 0, 0, 0.1) 0%, rgba(0, 0, 0, 0) 100%);
}

section.your-active-class .landing__container::before {
    opacity: 1;
    animation: rotate 4s linear 0s infinite forwards;
}

section.your-active-class .landing__container::after {
    opacity: 1;
    animation: rotate 5s linear 0s infinite forwards reverse;
}


@keyframes rotate {
    from {
        transform: rotate(0deg)
                   translate(-1em)
                   rotate(0deg);
    }
    to {
        transform: rotate(360deg)
                   translate(-1em) 
                   rotate(-360deg);
    }
}

<!DOCTYPE >
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Manipulating the DOM</title>
  <!-- Load Google Fonts -->
  <link href="https://fonts.googleapis.com/css?family=Fira+Sans:900|Merriweather&display=swap" rel="stylesheet">  <!-- Load Styles -->
  <link href="css/styles.css" rel="stylesheet">
  <script src="/js/app.js" defer></script>
</head>
<body>
  <!-- HTML Follows BEM naming conventions 
  IDs are only used for sections to connect menu achors to sections -->
  <header class="page__header">
    <nav class="navbar__menu">
      <!-- Navigation starts as empty UL that will be populated with JS -->
      <ul id="navbar__list"></ul>
    </nav>
  </header>
  <main>
    <header class="main__hero">
      <button id="newSection"> add section </button>
      <h1>Landing Page </h1>
    </header>
    <!-- Each Section has an ID (used for the anchor) and 
    a data attribute that will populate the li node.
    Adding more sections will automatically populate nav.
    The first section is set to active class by default -->
    <section id="section1" data-nav="Section 1" class="your-active-class">
      <div class="landing__container">
        <h2>Section 1</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi fermentum metus faucibus lectus pharetra dapibus. Suspendisse potenti. Aenean aliquam elementum mi, ac euismod augue. Donec eget lacinia ex. Phasellus imperdiet porta orci eget mollis. Sed convallis sollicitudin mauris ac tincidunt. Donec bibendum, nulla eget bibendum consectetur, sem nisi aliquam leo, ut pulvinar quam nunc eu augue. Pellentesque maximus imperdiet elit a pharetra. Duis lectus mi, aliquam in mi quis, aliquam porttitor lacus. Morbi a tincidunt felis. Sed leo nunc, pharetra et elementum non, faucibus vitae elit. Integer nec libero venenatis libero ultricies molestie semper in tellus. Sed congue et odio sed euismod.</p>

        <p>Aliquam a convallis justo. Vivamus venenatis, erat eget pulvinar gravida, ipsum lacus aliquet velit, vel luctus diam ipsum a diam. Cras eu tincidunt arcu, vitae rhoncus purus. Vestibulum fermentum consectetur porttitor. Suspendisse imperdiet porttitor tortor, eget elementum tortor mollis non.</p>
      </div>
    </section>
    <section id="section2" data-nav="Section 2">
      <div class="landing__container">
        <h2>Section 2</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi fermentum metus faucibus lectus pharetra dapibus. Suspendisse potenti. Aenean aliquam elementum mi, ac euismod augue. Donec eget lacinia ex. Phasellus imperdiet porta orci eget mollis. Sed convallis sollicitudin mauris ac tincidunt. Donec bibendum, nulla eget bibendum consectetur, sem nisi aliquam leo, ut pulvinar quam nunc eu augue. Pellentesque maximus imperdiet elit a pharetra. Duis lectus mi, aliquam in mi quis, aliquam porttitor lacus. Morbi a tincidunt felis. Sed leo nunc, pharetra et elementum non, faucibus vitae elit. Integer nec libero venenatis libero ultricies molestie semper in tellus. Sed congue et odio sed euismod.</p>

        <p>Aliquam a convallis justo. Vivamus venenatis, erat eget pulvinar gravida, ipsum lacus aliquet velit, vel luctus diam ipsum a diam. Cras eu tincidunt arcu, vitae rhoncus purus. Vestibulum fermentum consectetur porttitor. Suspendisse imperdiet porttitor tortor, eget elementum tortor mollis non.</p>
      </div>
    </section>
    <section id="section3" data-nav="Section 3">
      <div class="landing__container">
        <h2>Section 3</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi fermentum metus faucibus lectus pharetra dapibus. Suspendisse potenti. Aenean aliquam elementum mi, ac euismod augue. Donec eget lacinia ex. Phasellus imperdiet porta orci eget mollis. Sed convallis sollicitudin mauris ac tincidunt. Donec bibendum, nulla eget bibendum consectetur, sem nisi aliquam leo, ut pulvinar quam nunc eu augue. Pellentesque maximus imperdiet elit a pharetra. Duis lectus mi, aliquam in mi quis, aliquam porttitor lacus. Morbi a tincidunt felis. Sed leo nunc, pharetra et elementum non, faucibus vitae elit. Integer nec libero venenatis libero ultricies molestie semper in tellus. Sed congue et odio sed euismod.</p>

        <p>Aliquam a convallis justo. Vivamus venenatis, erat eget pulvinar gravida, ipsum lacus aliquet velit, vel luctus diam ipsum a diam. Cras eu tincidunt arcu, vitae rhoncus purus. Vestibulum fermentum consectetur porttitor. Suspendisse imperdiet porttitor tortor, eget elementum tortor mollis non.</p>
      </div>
    </section>
  </main>
  <footer class="page__footer">
    <p>&copy Udacity</p>
  </footer>

</body>
</html>

Answer 1

您的问题出在 buildNav 函数中的 section 变量，您必须重新搜索部分，否则您的变量 section 不会更新：


const buildNav = () => {
    navList.innerHTML ="";
    sections = document.querySelectorAll("section"); /* Reselect all sections */
    sections.forEach(section => { 
        const navItem = `<li><a class="menu__link" data-nav="${section.id}" href="${section.id}">${section.dataset.nav}</a></li>`
        navList.insertAdjacentHTML("beforeend",navItem)
    })
}

它确实添加了一个部分，但它不更新导航栏

it does add a section but it does not update the navbar

html

javascript

css

arrays

dynamic