1.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>打印倒正金字塔</title>
<style>
div{
text-align: center;
line-height: 25px;
}
hr{
width: 50px;
display: inline-block;
}
</style>
</head>
<body>
<div>
<h1>打印倒正金字塔直线</h1>
<script>
for (var i=7;i>0;i--){
for(var j=0;j<i;j++){
document.write("<hr/>")
}
document.write("<br/>")
}
for(var n=2;n<8;n++){
for(h=0;h<n;h++){
document.write("<hr/>")
}
document.write("<br/>")
}
</script>
</div>
</body>
</html>2.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var msg=prompt("请输入正确的邮箱地址","[email protected]");
if(msg.indexOf("@")!=-1 && msg.indexOf(".")!=-1){
alert("邮箱地址正确，邮箱名称是:"+msg.substring(0,msg.indexOf("@")));
}
else if(msg.length==0){
alert("邮箱不能为空!");
}
else{
alert("邮箱地址必须包含@和.");
}
</script>
</body>
</html>3.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var msg=prompt("请输入今天是星期几:");
switch(msg){
case "星期一":
alert("新的一周开始了");
break;
case "星期二":
case "星期三":
case "星期四":
alert("努力工作");
break;
case "星期五":
alert("明天就是周末了");
break;
default:
alert("放松的休息");
break;
}
</script>
</body>
</html>