代码1：
<!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" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
<title></title>
<style type="text/css"></style>
<script type="text/javascript">
window.onload = function() {
function countDown(){
var oSpan = document.getElementsByTagName("span");
var m = oSpan[0].innerHTML;
var n = oSpan[1].innerHTML;
var timer = setInterval(function(){
n--;
if(n % 60 == 0) {
m--;
n = m == 0 ? 0 : 60;
oSpan[1].innerHTML = n;
}
if(m == 0) {
clearTimeout(timer);
}
if(m >=0 && m <10) {
oSpan[0].innerHTML = "0" + m;
} else {
oSpan[0].innerHTML = m;
}
if (oSpan[1].innerHTML == 60) {
oSpan[1].innerHTML = "0" + 0;
} else if (n>=10 && n <=59) {
oSpan[1].innerHTML = n;
} else if (n>=0 && n<=9) {
oSpan[1].innerHTML = "0" + n;
}
}, 20);
};
countDown();
}
</script>
</head>
<body>
<span>1000</span>:<span>11</span>
</body>
</html>
代码2：
<!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" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
<title></title>
<style type="text/css"></style>
<script type="text/javascript">
window.onload = function() {
function countDown(){
var oSpan = document.getElementsByTagName("span");
var m = oSpan[0].innerHTML;
var n = oSpan[1].innerHTML;
var timer = setInterval(function(){
n--;
if(n % 60 == 0) {
m--;
n = m == 0 ? 0 : 60;
}
if(m == 0) {
clearTimeout(timer);
}
oSpan[0].innerHTML = m;
oSpan[1].innerHTML = n;
}, 1000);
};
countDown();
}
</script>
</head>
<body>
<span>12</span>:<span>11</span>
</body>
</html>
尝试运行下代码1和代码2，你会看到不同的效果。