简易的计时器实例，可以模拟注册协议倒计时同意
<!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>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript">
var a=3;
var jishi=function()
{
document.getElementById("agr").value = a+"秒后可以同意";
a--;
if(a ==0) {
clearTimeout(null);
document.getElementById("agr").style.color="red";
document.getElementById("agr").disabled=false;
document.getElementById("agr").value = "同意";
a=3;
}else{
setTimeout(jishi,1000);
}
}
function tongyi(){
alert("同意");
}
</script>
</head>
<body οnlοad="jishi()">
<input type="button" id="agr" disabled="disabled" οnclick="tongyi()" value="同意"/>
</body>
</html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript">
var a=3;
var jishi=function()
{
document.getElementById("agr").value = a+"秒后可以同意";
a--;
if(a ==0) {
clearTimeout(null);
document.getElementById("agr").style.color="red";
document.getElementById("agr").disabled=false;
document.getElementById("agr").value = "同意";
a=3;
}else{
setTimeout(jishi,1000);
}
}
function tongyi(){
alert("同意");
}
</script>
</head>
<body οnlοad="jishi()">
<input type="button" id="agr" disabled="disabled" οnclick="tongyi()" value="同意"/>
</body>
</html>
