为什么点返回键不直接跳转网页
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>编程练习</title>
</head>
<body>
<h1>操作成功</h1>
<span id="second">5</span>
<span>秒后返回主页</span>
<a href="javascript:back()">返回</a>
<script type="text/javascript">
var num =document.getElementById("second").innerHTML;
function count() {
num--;
document.getElementById("second").innerHTML=num;
if (num==0){
location.assign("http://www.imooc.com");
}
}
setInterval("count()",1000);
function back() {
window.history.back();
}
</script>
</body>
</html>为什么点返回键 不直接跳转网页
