Javascript 如果用户的页面宽度低于某个阈值，如何使用js更改html页面中的css文件

发布于12月18日

我想改变的css文件取决于如果用户是在移动或桌面上.我找不到任何实际工作的东西，所以我只是try 使用下面的js将用户重定向到一个带有diff css工作表的diff html页面.但我发现这超级低效.有没有人知道我怎样才能使css样式表根据页面中的屏幕宽度属性而改变？

<script type="text/javascript">
<!--
if (screen.width <= 699) {
document.location = "m_index.html";
}
//-->
</script>


       <!-- main css -->
       <link rel="stylesheet" href="master.css">
 
       <!-- CSS with media query -->
       <link rel="stylesheet"
             media="screen and (max-width: 360px)"
             href="small-screen.css">
       <link rel="stylesheet"
             media="screen and (min-width: 360px) and (max-width: 550px)"
             href="large-screen.css">

推荐答案

有响应式的设计是个好主意，但这是一种奇怪的方式.除非您使用JS来做这件事有一个非常好的理由，否则您可以用CSS来完成所有的工作，例如:https://www.w3schools.com/howto/howto_css_media_query_breakpoints.asp

在全屏模式下打开上面的代码片段，并调整窗口大小以查看演示.

有关更详细的文档，请参阅MDN page.

<!DOCTYPE html>
<!--copied from https://www.w3schools.com/howto/howto_css_media_query_breakpoints.asp-->
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.example {
  padding: 20px;
  color: white;
}
/* Extra small devices (phones, 600px and down) */
@media only screen and (max-width: 600px) {
  .example {background: red;}
}

/* Small devices (portrait tablets and large phones, 600px and up) */
@media only screen and (min-width: 600px) {
  .example {background: green;}
}

/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {
  .example {background: blue;}
} 

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {
  .example {background: orange;}
} 

/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) {
  .example {background: pink;}
}
</style>
</head>
<body>

<h2>Typical Breakpoints</h2>
<p class="example">Resize the browser window to see how the background color of this paragraph changes on different screen sizes.</p>

</body>
</html>