
<!DOCTYPE html>
<html>
<head>
<title>判断成绩等级</title>
</head>
<body>
<script>
var yw_num = prompt("请输入语文成绩");
var ss_num = prompt("请输入数学成绩");
var yy_num = prompt("请输入英语成绩");
var hx_num = prompt("请输入化学成绩");
var ls_num = prompt("请输入历史成绩");
var num = (parseInt(yw_num) + parseInt(ss_num) + parseInt(yy_num) + parseInt(hx_num) + parseInt(ls_num)) / 5;
switch (num) {
case num >= 90:
alert("优秀");
break;
case num >= 80:
alert("优良");
break;
case num >= 70:
alert("良好");
break;
case num >= 60:
alert("合格");
break;
default:
alert("不合格");
break;
}
</script>
</body>
</html>