求问js两个简单的练习

<html>
<head><title>练习题</title></head>
<body>
<script>
var arr = [0];
var x =0;
while(arr.length<7){
    var fen = parseFloat(prompt('请输入第'+arr.length+'个学生的成绩。'))
    if (!isNaN(fen)){
        arr.push(fen);
    }else{
        alert('录入信息格式错误，请重新录入')
    }
    if (fen<0){x++}
    arr[0] += fen
}
var sum = arr.shift();
document.write('七个学生总分为'+sum)
document.write('七个学生平均分为'+(sum/7))
document.write('不及格学生有'+x)
</script>
</body>
</html>

输入是用prompt().,还是文本框？

<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
	<title> 页面名称 </title>
</head>
<body>

<script type="text/javascript">
var arr = [];
var sum = 0;
for (var i = 0; i < 7; i++) {
	arr[i] = parseFloat(prompt("请输入第"+(i+1)+"个学生成绩：",""));
	sum += arr[i];
}
var div = document.createElement("div");
div.innerHTML = "总分："+sum;
document.body.appendChild(div);
var div = document.createElement("div");
div.innerHTML = "平均分："+sum/7;
document.body.appendChild(div);
var h = 0;
for (var i = 0; i < 7; i++) {
	if (arr[i]<60) {
		var div = document.createElement("div");
		div.innerHTML = "不及格的成绩"+arr[i];
		document.body.appendChild(div);
		h++;
	}
}
var div = document.createElement("div");
div.innerHTML = "不及格的数量"+h;
document.body.appendChild(div);

</script>


</body>
</html>

<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
	<title> 页面名称 </title>
</head>
<body>

<script type="text/javascript">
var s = parseFloat(prompt("请输入商品总价：",""));
var div = document.createElement("div");
if (s >= 500) {
	div.innerHTML = "8折商品总价："+s*0.8;
} else {
	div.innerHTML = "不打折商品总价："+s;
	
}
document.body.appendChild(div);

</script>


</body>
</html>

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