<html>
<head>
<title>gallery</title>
<style>
.change{
background:red;
}
.change2{
background:black;
}
</style>
</head>
<body id="body1" class="change" onclick="changeColor()">
</body>
</html>
<script>
function changeColor(){
var style = document.getElementById("body1").className;
if(style=="change"){
document.getElementById("body1").className = "change2";
}else{
document.getElementById("body1").className = "change";
}
}
</script>
小练习，点击背景改变颜色。