1、element.style(用于设置简单的样式)
2、element.className(用于设置复杂的样式)
案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.first {
width: 200px;
height: 200px;
background-color: aqua;
}
.change {
width: 100px;
height: 100px;
background-color: blue;
}
</style>
</head>
<body>
<div class="first"></div>
<script>
var C = document.querySelector('.first');
C.onclick = function () {
this.className = 'change';
}
</script>
</body>
</html>