遇到此错误：未捕获的类型错误：无法在 HTMLDivElement.<anonymous> 处读取 null 的属性“classList”答案

【问题标题】：Stuck at this error: Uncaught TypeError: Cannot read property 'classList' of null at HTMLDivElement.<anonymous>遇到此错误：未捕获的类型错误：无法在 HTMLDivElement.<anonymous> 处读取 null 的属性“classList”
【发布时间】：2020-12-24 13:23:54
【问题描述】：

我开始尝试在 VS Code 中编写一些东西，我想我可以尝试制作一个移动 GUI，但是由于一些错误，我无法在 JavaScript 中打开菜单（从第 230 行开始，第 238 行的问题）：

未捕获的类型错误：无法在 HTMLDivElement 处读取 null 的属性“classList”。

我知道发生了什么，但我不知道如何让它发挥作用。

这是我目前编写的脚本：

const navSlide = () => {
    const burger = document.querySelector('.burger');
    const nav = document.querySelector('.nav_links');

    burger.addEventListener('click', () => {
        nav.classList.toggle('nav-active');
    });
}

navSlide();

@import url('https://fonts.googleapis.com/css2?family=Montserrat:wght@500&display=swap');

    .Buton_YT {
        font-size: 34px;
        padding: 5px 10px;
        border: 3px solid #000000;
        border-radius: 5px  ;
        text-decoration: none;
        display: inline-block;
        color: #09ff00;
        transition-duration: 0.2s;
        background-color: none;
        width: 120px;
        text-align: center;
        cursor: none;
        position: absolute;
        top: 30px;
        font-family: 'arial', cursive;
    }

    ::selection {
        color:white;
        background-color: rgb(60, 255, 0);
    }

    .Buton_YT:hover {
        color: #ffffff;
        background-color: #ff0000;
        box-shadow: 5px #000000;
    }

    .Buton_YT:active {
        transition-duration: 100ms;
        background-color: #ff0000;
        box-shadow: 0 5px rgb(20, 20, 20);
        transform: translateY(4px);
    }
    
    .div1 {
        width: 500;
        height: 100;
        color: #00ffff;
        display: inline-block;
        position: absolute;

    }


* {
    box-sizing: border-box;
    margin: 0px;
    padding: 0px;
    background-color: #333333;
}

li, a, .Buton_YT{
    font-family: "Montserrat", sans-serif;
    font-weight: 500;
    font-size: 18px;
    color: #edf0f1;
    text-decoration: none;
    justify-content: end;
} 

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 3px 1%;
    border: black 2px solid;
    background-color:  #202020;
}

nav {
    background-color: #202020;
}


.logo {
    cursor: not-allowed;
    margin-right: auto;
}

/*.name {
    cursor: not-allowed;
    margin-right: flex-end;
}*/

.nav__links {
    list-style: none;
    background-color:  #202020;
}

.nav__links li {
    display: inline-block;
    padding: 0px 20px;
    background-color:  #202020;
}

.nav__links li a {
    transition-delay: 500ms;
    transition: all 0.2s ease 0s;
    background-color:  #202020;
}

.nav__links li a:hover {
    color: rgba(0, 128, 160, 0.6);
}

.nav__links li a:active {
    color: rgba(0, 136, 169, 0.1);
    transition: all 0.001s ease 0s;
}

.buton_nav {
    padding: 9px 20px;
    background-color: rgba(0, 136, 169, 1);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: all 0.3s;
}

.buton_nav:hover {
    background-color: rgba(0, 128, 160, 0.6);
    transition: all 0.1s ease 0s;
}

.buton_nav:active {
    background-color: rgba(0, 136, 169, 0.3);
}

.burger{
    display: none;
    cursor: pointer;
}

.burger div {
    width: 25px;
    height: 3px;
    background-color: rgb(255, 255, 255);
    margin: 5px;
    border-radius: 10px;
    color: #202020;
}

@media screen and (max-width: 720px) {
    body {
        overflow-x: hidden;
    }

    .nav__links{
        position: absolute;
        right: 00px;
        height: 92vh;
        top: 54.5px;
        background-color: #202020;
        display: flex;
        flex-direction: column;
        align-items: center;
        width: 150px;
        transform: translateX(100%);
        line-height: 110px;
        transition: transform 0.5 ease-in;
    }

    .nav__links li {
        opacity: 30%;
    }

    .burger{
        display: block;
        background-color: #202020;
    }

}

.nav-active {
    transform: translateX(0px);
}

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>TESTE 2</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <header>
            <img class="logo" src="Logo.jpg" alt="logo" width="80px" height="45px"><img>
            <div class="name">
                <h4 class="name"> </h4>
            </div>
            <nav>
                <ul class="nav__links">
                    <li>
                        <a href="Projects.html">Proiecte</a>
                    </li>
                    <li>
                        <a href="About.html">Despre</a>
                    </li>
                    <li>
                        <a href="Pagini.html">Pagini</a>
                    </li>
                    <li>
                        <a href="test_2.html">Acasa</a>
                    </li>
                </ul>
                <div class="burger">
                    <div class="burger1"></div>
                    <div class="burger2"></div>
                    <div class="burger3"></div>
                </div>
            </nav>
            <a class="buton_nav" href="Contact.html">Contact</a>
        </header>
    </head>
    <body>

<p>Text to test selection colors</p>

<div class="div1">

    <a button class="Buton_YT" href="#" target="_blank">Buton YT</a>

</div>


</body>
</html>

【问题讨论】：

你应该在部分写你的
元素
<ul class="nav__links"> 有 2 个下划线。当您搜索 document.querySelector('.nav_links') 时，您只有 1 个。
为什么会有两个</body>标签？
...<head>...</head> 标记中不应有任何标记。
如果您将 document.querySelector('.nav_links') 更改为 document.querySelector('.nav__links') 投票关闭，则由于拼写错误

标签： javascript html css dom-events

【解决方案1】：

<html lang="en">
  <head>
<title>TESTE 2</title>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<style>
  @import url("https://fonts.googleapis.com/css2?family=Montserrat:wght@500&display=swap");

  .Buton_YT {
    font-size: 34px;
    padding: 5px 10px;
    border: 3px solid #000000;
    border-radius: 5px;
    text-decoration: none;
    display: inline-block;
    color: #09ff00;
    transition-duration: 0.2s;
    background-color: none;
    width: 120px;
    text-align: center;
    cursor: none;
    position: absolute;
    top: 30px;
    font-family: "arial", cursive;
  }

  ::selection {
    color: white;
    background-color: rgb(60, 255, 0);
  }

  .Buton_YT:hover {
    color: #ffffff;
    background-color: #ff0000;
    box-shadow: 5px #000000;
  }

  .Buton_YT:active {
    transition-duration: 100ms;
    background-color: #ff0000;
    box-shadow: 0 5px rgb(20, 20, 20);
    transform: translateY(4px);
  }

  .div1 {
    width: 500;
    height: 100;
    color: #00ffff;
    display: inline-block;
    position: absolute;
  }

  * {
    box-sizing: border-box;
    margin: 0px;
    padding: 0px;
    background-color: #333333;
  }

  li,
  a,
  .Buton_YT {
    font-family: "Montserrat", sans-serif;
    font-weight: 500;
    font-size: 18px;
    color: #edf0f1;
    text-decoration: none;
    justify-content: end;
  }

  header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 3px 1%;
    border: black 2px solid;
    background-color: #202020;
  }

  nav {
    background-color: #202020;
  }

  .logo {
    cursor: not-allowed;
    margin-right: auto;
  }

  /*.name {
  cursor: not-allowed;
  margin-right: flex-end;
}*/

  .nav__links {
    list-style: none;
    background-color: #202020;
  }

  .nav__links li {
    display: inline-block;
    padding: 0px 20px;
    background-color: #202020;
  }

  .nav__links li a {
    transition-delay: 500ms;
    transition: all 0.2s ease 0s;
    background-color: #202020;
  }

  .nav__links li a:hover {
    color: rgba(0, 128, 160, 0.6);
  }

  .nav__links li a:active {
    color: rgba(0, 136, 169, 0.1);
    transition: all 0.001s ease 0s;
  }

  .buton_nav {
    padding: 9px 20px;
    background-color: rgba(0, 136, 169, 1);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: all 0.3s;
  }

  .buton_nav:hover {
    background-color: rgba(0, 128, 160, 0.6);
    transition: all 0.1s ease 0s;
  }

  .buton_nav:active {
    background-color: rgba(0, 136, 169, 0.3);
  }

  .burger {
    display: none;
    cursor: pointer;
  }

  .burger div {
    width: 25px;
    height: 3px;
    background-color: rgb(255, 255, 255);
    margin: 5px;
    border-radius: 10px;
    color: #202020;
  }

  @media screen and (max-width: 720px) {
    body {
      overflow-x: hidden;
    }

    .nav__links {
      position: absolute;
      right: 00px;
      height: 92vh;
      top: 54.5px;
      background-color: #202020;
      display: flex;
      flex-direction: column;
      align-items: center;
      width: 150px;
      transform: translateX(100%);
      line-height: 110px;
      transition: transform 0.5 ease-in;
    }

    .nav__links li {
      opacity: 30%;
    }

    .burger {
      display: block;
      background-color: #202020;
    }
  }

  .nav-active {
    transform: translateX(0px);
  }
</style>
  </head>
  <body>
    <header>
  <img
    class="logo"
    src="Logo.jpg"
    alt="logo"
    width="80px"
    height="45px"
  /><img />
  <div class="name">
    <h4 class="name"></h4>
  </div>
  <nav>
    <ul class="nav__links">
      <li>
        <a href="Projects.html">Proiecte</a>
      </li>
      <li>
        <a href="About.html">Despre</a>
      </li>
      <li>
        <a href="Pagini.html">Pagini</a>
      </li>
      <li>
        <a href="test_2.html">Acasa</a>
      </li>
    </ul>
    <div class="burger">
      <div class="burger1"></div>
      <div class="burger2"></div>
      <div class="burger3"></div>
    </div>
  </nav>
  <a class="buton_nav" href="Contact.html">Contact</a>
    </header>
    <p>Text to test selection colors</p>

    <div class="div1">
      <a button class="Buton_YT" href="#" target="_blank">Buton YT</a>
    </div>

    <script>
      const navSlide = () => {
        const burger = document.querySelector(".burger");
        const nav = document.querySelector(".nav__links");

        burger.addEventListener("click", () => {
          nav.classList.toggle("nav-active");
        });
      };

      navSlide();
    </script>
  </body>
</html>

【讨论】：