start按钮中,为什么写onclick="clock()"不起效,而是要重新定义一个函数才起效呢
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>计时器</title>
<script type="text/javascript">
function clock(){
var time=new Date();
document.getElementById("clock").value = time;
}
var i = setInterval("clock()",1000); //每隔1秒就是执行一次clock()函数,并将返回值赋值给i
</script>
</head>
<body>
<form>
<input type="text" id="clock" size="50" />
<input type="button" value="Stop" onclick="clearInterval(i)"/>
<input type="button" value="Start" onclick="clock()"/>
</form>
</body>
</html>