示例代码：
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>test</title><style>.border{width: 100px;height: 100px;background-color: red;}.border:hover{background-color: green !important;}</style><script>function changeBackgroundColor(){document.getElementById("border").style.backgroundColor="blue";}</script>
</head>
<body><div id="border" class="border" οnclick="changeBackgroundColor()"></div>
</body>
</html>