我是初学者，面临javascript和html链接的问题。Can'；在HTML中看不到javascript的效果_Javascript_Html_Dom_Javascript Events_Javascript Objects

我是初学者，面临javascript和html链接的问题。Can'；在HTML中看不到javascript的效果

javascript html dom

我是初学者，面临javascript和html链接的问题。Can'；在HTML中看不到javascript的效果,javascript,html,dom,javascript-events,javascript-objects,Javascript,Html,Dom,Javascript Events,Javascript Objects,我已经创建了一个admin.html文件，其中h1标记中有div类。我已经使用script:src连接了admin.js文件，但是当我在javascript中更改颜色时，无法看到效果。但当我在chrome中检查时，同样的代码也在工作。谢谢你的帮助 admin.html <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8">

我已经创建了一个admin.html文件，其中h1标记中有div类。我已经使用script:src连接了admin.js文件，但是当我在javascript中更改颜色时，无法看到效果。但当我在chrome中检查时，同样的代码也在工作。谢谢你的帮助

admin.html

<!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>Admin</title>
    <link rel="stylesheet" href="style2.css">
    <script src="admin.js"></script>  
</head>
<body>
  <ul class="list"> 
    <li id="dashbord"style="font-size: 40px; padding-top: 8px; height: 50px;"><a  href="#dashbord">Dashboard</a></li>
    <br>
    <li><a class="active" href="#home">Home</a></li>
    <li><a href="#contact">Contact</a></li>
    <li><a href="#about">About</a></li>
  </ul>
  <div class="div" style="margin-left:25%;padding:1px 16px;height:1000px;">
    <h2>Fixed Full-height Side Nav</h2>
    <h3>Try to scroll this area, and see how the sidenav sticks to the page</h3>
    <p>Notice that this div element has a left margin of 25%. This is because the side navigation is set to 25% width. If you remove the margin, the sidenav will overlay/sit on top of this div.</p>
    <p>Also notice that we have set overflow:auto to sidenav. This will add a scrollbar when the sidenav is too long (for example if it has over 50 links inside of it).</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
  </div>
  
</body>
</html>

原因是在读取HTML文件和构建DOM之前，会对脚本进行解析和计算。DOM元素当时不存在

将

脚本

标记移动到

正文

的末尾

<!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>Admin</title>
    <link rel="stylesheet" href="style2.css">
</head>
<body>
  <ul class="list"> 
    <li id="dashbord"style="font-size: 40px; padding-top: 8px; height: 50px;"><a  href="#dashbord">Dashboard</a></li>
    <br>
    <li><a class="active" href="#home">Home</a></li>
    <li><a href="#contact">Contact</a></li>
    <li><a href="#about">About</a></li>
  </ul>
  <div class="div" style="margin-left:25%;padding:1px 16px;height:1000px;">
    <h2>Fixed Full-height Side Nav</h2>
    <h3>Try to scroll this area, and see how the sidenav sticks to the page</h3>
    <p>Notice that this div element has a left margin of 25%. This is because the side navigation is set to 25% width. If you remove the margin, the sidenav will overlay/sit on top of this div.</p>
    <p>Also notice that we have set overflow:auto to sidenav. This will add a scrollbar when the sidenav is too long (for example if it has over 50 links inside of it).</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
  </div>
  
  <script src="admin.js"></script>  
</body>
</html>

将

脚本

标记移动到

正文

的末尾。有些框架，比如Webpack，会在头部添加

脚本

标记，并添加

延迟

，但我不确定这是否总是有效。用标准元素类型命名类是相当混乱的。我不建议你那样做。还将学习如何在浏览器中使用开发人员工具。您的代码打印的错误消息是一个很有用的搜索词，可以在Google中键入。

<!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>Admin</title>
    <link rel="stylesheet" href="style2.css">
</head>
<body>
  <ul class="list"> 
    <li id="dashbord"style="font-size: 40px; padding-top: 8px; height: 50px;"><a  href="#dashbord">Dashboard</a></li>
    <br>
    <li><a class="active" href="#home">Home</a></li>
    <li><a href="#contact">Contact</a></li>
    <li><a href="#about">About</a></li>
  </ul>
  <div class="div" style="margin-left:25%;padding:1px 16px;height:1000px;">
    <h2>Fixed Full-height Side Nav</h2>
    <h3>Try to scroll this area, and see how the sidenav sticks to the page</h3>
    <p>Notice that this div element has a left margin of 25%. This is because the side navigation is set to 25% width. If you remove the margin, the sidenav will overlay/sit on top of this div.</p>
    <p>Also notice that we have set overflow:auto to sidenav. This will add a scrollbar when the sidenav is too long (for example if it has over 50 links inside of it).</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
  </div>
  
  <script src="admin.js"></script>  
</body>
</html>

<!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>Admin</title>
    <link rel="stylesheet" href="style2.css">
    <script src="admin.js" defer></script>  
</head>
<body>
  <ul class="list"> 
    <li id="dashbord"style="font-size: 40px; padding-top: 8px; height: 50px;"><a  href="#dashbord">Dashboard</a></li>
    <br>
    <li><a class="active" href="#home">Home</a></li>
    <li><a href="#contact">Contact</a></li>
    <li><a href="#about">About</a></li>
  </ul>
  <div class="div" style="margin-left:25%;padding:1px 16px;height:1000px;">
    <h2>Fixed Full-height Side Nav</h2>
    <h3>Try to scroll this area, and see how the sidenav sticks to the page</h3>
    <p>Notice that this div element has a left margin of 25%. This is because the side navigation is set to 25% width. If you remove the margin, the sidenav will overlay/sit on top of this div.</p>
    <p>Also notice that we have set overflow:auto to sidenav. This will add a scrollbar when the sidenav is too long (for example if it has over 50 links inside of it).</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
    <p>Some text..</p>
  </div>
  
</body>
</html>