CSS部分:
<style>.p::after{
content: "Hello"
color: red
}
</style>
JS部分:
<script>var p = document.querySelector('p')
p.setAttribute('class','p')
</script>
HTML部分:
<p></p>方法一,完全用js模拟(这样太麻烦)
<!DOCTYPE html><html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.css1{
width: 100px
height: 200px
border: 1px solid black
}
.css1:hover
{
border: 2px solid red
}
</style>
</head>
<body>
<div>这是一个div</div>
<script>
var div = document.getElementsByTagName("div")[0]
div.style.cssText = "border:1px solid redwidth:100pxheight:100px"
div.onmouseover = function () {
div.style.cssText = "border:1px solid blackwidth:100pxheight:100px"
}
div.onmouseout = function () {
div.style.cssText = "border:1px solid redwidth:100pxheight:100px"
}
</script>
</body>
</html>
2.方法二:js加css,还是麻烦
<!DOCTYPE html><html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.css1{
width: 100px
height: 200px
border: 1px solid black
}
.css1:hover
{
border: 2px solid red
}
</style>
</head>
<body>
<div>这是一个div</div>
<script>
// var div = document.getElementsByTagName("div")[0]
// div.style.cssText = "border:1px solid redwidth:100pxheight:100px"
// div.onmouseover = function () {
// div.style.cssText = "border:1px solid blackwidth:100pxheight:100px"
// }
// div.onmouseout = function () {
// div.style.cssText = "border:1px solid redwidth:100pxheight:100px"
// }
var div = document.getElementsByTagName("div")[0]
div.setAttribute("class","css1")
</script>
</body>
</html>
其实完全可以不用js来设置css,这样会比较麻烦,最直接的方法就是在元素里面直接设置class,在style或者css文件里面定义样式,如果有伪类这些也可以写在里面就好。