📄 21.4.htm
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Cookie Customization Example</title>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<script type="text/javascript">
<!--
var cookies = new Object(); //创建一个新对象
function extractCookies()
{ //定义几个变量，备用
var name, value;
var beginning, middle, end;
for (name in cookies)
{ //如果有多个条目，则将其删除
cookies = new Object();
break;
}
beginning = 0; // 从Cookie字符串的头部开始
while (beginning < document.cookie.length)
{
middle = document.cookie.indexOf('=', beginning);
end = document.cookie.indexOf(';', beginning);
if (end == -1) //如果没有分号（;），则此为最后一个Cookie
end = document.cookie.length;
if ( (middle> end) || (middle == -1) ){
// 如果该Cookie没有值
name = document.cookie.substring(beginning, end); //取其名称
value = "";
}
else{
// 析取该值
name = document.cookie.substring(beginning, middle); //取其名称
value = document.cookie.substring(middle + 1, end); //取其值
}
cookies[name] = unescape(value); // 添加至关联数组
beginning = end + 2; // 跳至下一Cookie的开始位置
}
}
function changeColors(scheme) //函数：改变颜色
{
switch(scheme) {
//根据不同的选项，设置不同的背景色和前景色
case "plain": foreground = "black"; background = "white"; break;
case "ice": foreground = "lightblue"; background = "darkblue"; break;
case "green": foreground = "white"; background = "darkgreen"; break;
default: return;
}
document.bgColor = background; //设置背景色
document.fgColor = foreground; //设置前景色
}
function changeScheme(which)
{
document.cookie = "cookiesenabled=true";
extractCookies();
if (!cookies["cookiesenabled"]) {
//如果禁用Cookie，则给出提示
alert("You need to enable cookies for this demo!");
return; //返回
}
document.cookie = "scheme=" + which; //设置Cookie
changeColors(which); //改变颜色
}
var pageLoaded = false;
extractCookies();
changeColors(cookies["scheme"]); //调用changeColors()改变颜色
//-->
</script>
</head>
<body onload="pageLoaded=true">
<h1>Customization Example</h1>
<hr>
<!--添加一段文字，以观察效果-->
<blockquote>
Where a calculator on the ENIAC is equipped with
19,000 vacuum tubes and weighs 30 tons, computers in the future may
have only 1,000 vacuum tubes and perhaps only weigh 1.5 tons.
</blockquote>
<em>from Popular Mechanics, March 1949.</em>
<hr>
<!--控制表单-->
<form action="#" method="get">改变背景颜色方案:
<!--分别通过onclick调用changeScheme()函数，改变页面色彩方案-->
<input type="button" value="无格式" onclick="changeScheme('plain');">
<input type="button" value="蓝色" onclick="changeScheme('ice');">
<input type="button" value="绿色" onclick="changeScheme('green');">
</form>
</body>
</html>
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