难得听课（小声bb）
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>随机更改背景颜色</title>
<script type="text/javascript">
var table,color;
function $(id){return document.getElementById(id);}
function randomInt(){
var rancor=Math.floor(Math.random()*256);
return rancor;
}
function ChangeColor(){
table=$("FirstTab");
color=table.getAttribute("bgcolor");//保存原始值
var r=randomInt().toString(16);///转化为16进制
var g=randomInt().toString(16);
var b=randomInt().toString(16);
var rescolor="#"+r+g+b;
table.setAttribute("bgcolor",rescolor);///把后者的值赋值给前者
}
function ResetColor(){
///color="#179BD6";
table.setAttribute("bgcolor",color);
}
</script>
</head>
<body>
<form method="post" >
<table align="center" border="1" bgcolor="#179BD6" width="500px" id="FirstTab">
<tr>
<caption>学生花名册</caption>
<td>序号</td>
<td>姓名</td>
<td>学号</td>
<td>专业</td>
</tr>
<tr>
<td>1</td>
<td>Cutele</td>
<td>261</td>
<td>软件工程</td>
</tr>
<tr>
<td>2</td>
<td>小乐乐</td>
<td>20192203262</td>
<td>网络工程</td>
</tr>
<tr>
<td colspan="4">
<input type="button" value="change color" onClick="ChangeColor()">
<input type="button" value="reset color" onClick="ResetColor()">
</td>
</tr>
</table>
</form>
</body>
</html>