1、源码
<!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">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>JavaScript</title>
<script type="text/javascript">
var score = prompt("请输入一个分数","");
if(!score){
alert("您没有输入值！");
}else{
score *= 1;
if(isNaN(score))
{
alert("您输入不合法的值！");
}else{
if(score >= 0 && score < 60)
{
alert("E");
}else{
if(score >= 60 && score < 70)
{
alert("D");
}else{
if(score >= 70 && score < 80)
{
alert("C");
}else{
if(score >= 80 && score < 90)
{
alert("B");
}else{
if(score >= 90 && score <= 100)
{
alert("A");
}
}
}
}
}
}
}
</script>
</head>
<body>
</body>
</html>