开启定时器: 两种方式
setInterval(函数名，间隔时间) 间隔型
setTimeout(函数名，间隔时间) 延时型
示例1
<!DOCTYPE HTML>
<html>
<head>
<meta charset = "utf-8">
<title>无标题</title>
<script>
function show(){
alert("a");
}
setInterval(show,1000);
</script>
<body>
</body>
</html>
``````````````````````````````````````````
示例2
<!DOCTYPE HTML>
<html>
<head>
<meta charset = "utf-8">
<title>无标题</title>
<script>
function show(){
alert("a");
}
setTimeout(show,1000);
</script>
<body>
</body>
</html>
·········································
关闭定时器：
clearInterval
clearTimeout
示例3
<!DOCTYPE HTML>
<html>
<head>
<meta charset = "utf-8">
<title>无标题</title>
<script>
window.onload=function(){
var obtn1 = document.getElementById('btn1');
var obtn2 = document.getElementById('btn2');
var schedule1 = null;
obtn1.onclick=function(){
alert("aa");
schedule1 = setInterval(function(){
alert("schedule1 is running");
},1000);
};
obtn2.onclick=function(){
clearInterval(schedule1);
};
}
</script>
<body>
<div>
<input type="button" id="btn1" value="开启"/>
<input type="button" id="btn2" value="关闭"/>
</div>
</body>
</html>
``````````````````````````````````````````````````````````
示例：数码时钟
<!DOCTYPE HTML>
<html>
<head>
<meta charset = "utf-8">
<title>无标题</title>
<script>
window.onload=function(){
var imgs = document.getElementsByTagName('img');
function toDouble(n){
if(n<10){
return '0'+n;
}else{
return ''+n;
}
}
function watch(){
var oDate = new Date();
var str = toDouble(oDate.getHours()) + toDouble(oDate.getMinutes()) + toDouble(oDate.getSeconds());
for(var i = 0 ; i < imgs.length;i++){
imgs[i].src = "images/" +str[i]+ ".png"; // str[i] 也可以用 str.charAt(i)
}
}
setInterval(watch,1000);
watch();
}
</script>
<body style="background:black; color:white; font-size=50px;" >
<img src="images/0.png"/>
<img src="images/0.png"/>
:
<img src="images/0.png"/>
<img src="images/0.png"/>
:
<img src="images/0.png"/>
<img src="images/0.png"/>
</body>
</html>
//图片自己找个 从 1-9的图片吧 放在 image 文件夹下面