我是一个菜鸟，到目前为止，我很难理解如何用我有限的学习来做到这一点。任务是将输入的gpa从高到低排序，给出平均值，提取最高和最低，并分离并输出所有高于3.4的gpa。我可以做到这一点。我的问题是，如果没有高于 3.4 的 GPA，我试图输出一个字符串，说明"今年没有好学生"，并且我用头撞墙几个小时。谁能帮忙？ 这是代码和我的笔记：
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<div id="output">
</div>
<script>
var gpasOut = [];
var gpas = [];
while (gpasOut != "XXX")
{
gpasOut = prompt("Enter a GPA or XXX to Stop");
if (gpasOut != "XXX")
{
gpas.push(parseFloat(gpasOut));
}
}
// This sets the vars as empty and prompts the user for integers and allows a break with "XXX";
// gpas.push pushes the values from the prompt (gpasOut) into gpas &
// parseFloat turns the strings into floating decimals;
length = gpas.length;
// This gets the number of integers entered at prompt.
function totalArray(total, num)
{
return total + num;
}
var total = gpas.reduce(totalArray);
// This gets the sum of all numbers in array. Not sure I understand this code, but I was able to make it work.
// I think it brings the numbers from the right (num) into the number on the left (total), thus "reducing" it.
//
// I'm sure there is a better way.
var average = total / length;
// This gives the average GPA
var sorted = gpas.sort(function (a, b)
{
return b - a
});
// This sorts the GPAs highest to lowest. Not sure I understand how it works.
var badGpas = "<p>There were no good students this year. Try again next year!</p>";
let goodGpas = [];
for (let i = 0; i < gpas.length; i++)
{
if (gpas[i] >= 3.4)
{
goodGpas.push(gpas[i]);
}
else {
badGpas
}
}
// Here I want to print the string in BadGpas if there were NO gpas above 3.4!
document.getElementById('output').innerHTML =
"<h2>GPAs</h2><h3>Sorted Highest to Lowest: </h3>" + sorted.join("<br>")
+"<h3>Class Average GPA is</h3>" + average + "<br>"
+ "<h3>The Highest is:</h3>" + gpas[0]
+ "<h3>The Lowest is:</h3>" + gpas[gpas.length-1]
+ "<h3>Outstanding GPAs (above 3.4)</h3>" + goodGpas.join("<br>")+badGpas;
</script>
</body>
</html>
基于您所拥有的，您可以将 badGpas 变量初始化为空字符串：
let badGpas = '';
然后，在检查循环中的 gpas 并将所有高于 3.4 的 gpas 推送到 goodGpas 数组后，您可以检查该数组是否为空。如果数组为空，则将 badGpas 值设置为要显示的文本：
let badGpas = '';
let goodGpas = [];
for (let i = 0; i < gpas.length; i++)
{
if (gpas[i] >= 3.4)
{
goodGpas.push(gpas[i]);
}
}
if (goodGpas.length === 0) {
badGpas = "<p>There were no good students this year. Try again next year!</p>";
}
已修复：
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<div id="output">
</div>
<script>
var gpasOut = [];
var gpas = [];
while (gpasOut != "XXX")
{
gpasOut = prompt("Enter a GPA or XXX to Stop");
if (gpasOut != "XXX")
{
gpas.push(parseFloat(gpasOut));
}
}
// This sets the vars as empty and prompts the user for integers and allows a break with "XXX";
// gpas.push pushes the values from the prompt (gpasOut) into gpas &
// parseFloat turns the strings into floating decimals;
length = gpas.length;
// This gets the number of integers entered at prompt.
function totalArray(total, num)
{
return total + num;
}
var total = gpas.reduce(totalArray);
// This gets the sum of all numbers in array. Not sure I understand this code, but I was able to make it work.
// I think it brings the numbers from the right (num) into the number on the left (total), thus "reducing" it.
//
// I'm sure there is a better way.
var average = total / length;
// This gives the average GPA
var sorted = gpas.sort(function (a, b)
{
return b - a
});
// This sorts the GPAs highest to lowest. Not sure I understand how it works.
var foundGpasAbove = false
let goodGpas = [];
for (let i = 0; i < gpas.length; i++)
{
if (gpas[i] >= 3.4)
{
foundGpasAbove = true;
goodGpas.push(gpas[i]);
}
}
// Here I want to print the string in BadGpas if there were NO gpas above 3.4!
if(foundGpasAbove) {
document.getElementById('output').innerHTML =
"<h2>GPAs</h2><h3>Sorted Highest to Lowest: </h3>" + sorted.join("<br>")
+"<h3>Class Average GPA is</h3>" + average + "<br>"
+ "<h3>The Highest is:</h3>" + gpas[0]
+ "<h3>The Lowest is:</h3>" + gpas[gpas.length-1]
+ "<h3>Outstanding GPAs (above 3.4)</h3>";
} else {
document.getElementById('output').innerHTML = '<p>There were no good students this year. Try again next year!</p>'
}
</script>
</body>
</html>
解释： 我放了一个标志发现 GpasAbove 在循环之前初始化为 false，如果它超过 3.4，则添加 gpas。如果你添加一个，那么我使这个标志为真。在使用此标志之后，如果为假，我会打印您想要的消息"今年没有好学生。明年再试！