<!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>test</title>
</head>
<style>
.s1 {
border: 1px solid red;
}
.s2 {
font-size: 100px;
}
.s3 {
background-color: rgb(21, 202, 36);
}
</style>
<body>
<div class="s1" id="div1">
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
</div>
<script>
let div = document.getElementById("div1");
//这样会把div1 原来的s1样式覆盖，只有s2
div.setAttribute("class", "s2");
//这样是在原来的基础上追加 s2和s3 最后会同时有test1,test2,test3样式
div.classList.add("s2", "s3");
//移除test1样式
div.classList.remove("s1");
//同时移除多个样式s1,s2
div.classList.remove("s1", "s2");
//判断是否包含s1样式
div.classList.contains("s1");
</script>
</body>
</html>
