我希望能够让用户输入多个成绩，然后使用Javascript来平均输入的成绩。当用户输入成绩后，他们可以单击取消并关闭Propmt Box，如果他们根本不输入任何成绩（默认为0），则程序会显示没有输入成绩。
我对此非常陌生！我在我的大学读了一个javascript课程，这有点令人困惑，因为老师没有教！我们所要提到的只是W3schools，这些东西根本没有列出！
以下是另一种解释： ＆＃34;开发一个程序，允许教师输入任意数量的成绩，进行平均计算，然后用语法句子显示结果。该程序还必须告诉用户是否没有输入成绩。您需要使用循环和“if else”语句。一定要声明所有变量并测试除以零的可能性。＆＃34;
<script type = "text/javascript">
var gradeCounter = 0,
gradeValue = 0,
total = 0,
average, grade;
var sum = 0;
var i = 0;
while (gradeValue != -1 && gradeValue <= 100) {
//Prompt the user
grade = prompt("Enter Grades, -1 to Quit:", "0");
//Parse the prompt result to a int
sum += parseInt(grade);
i++;
if (i >= 0 && grade != null) {
document.getElementById("average").innerHTML = "The average of the grades you've entered are " + sum / i + ".";
} else {
document.getElementById("error").innerHTML = "There were no grades entered";
}
} </script>
再次感谢！
答案 0 :(得分：1)
// note: the dom must be ready before execution
var btn = document.querySelector('button'),
res = document.getElementById('average');
btn.addEventListener('click', function(e) {
var val = prompt('Enter comma delimited grades to average');
val = val.length ? val.replace(/\s/g, '').split(',') : '';
var count = val.length || 0; // no 0 division
if (!count) {
res.innerHTML = 'you must enter comma delimited numbers to average';
return;
} else {
var average = val.reduce(function(a, b) { // is a loop
return +a + +b;
});
res.innerHTML = (average /= count).toFixed(1);
}
});
HTML
<button id="avgBtn">Prompt</button>
<p>Average: <span id="average"></span></p>
答案 1 :(得分：1)
var grades = [];
// initialize the array that will store the entries
var sum = 0;
// initialize the variable that will add the array values together
var average;
// initialize the variable that will contain the final result
var invalid = [];
// initialize the variable that will be used to make sure the user inserts something
for (i = 0; i < 5; i++) {
// repeat the following code 5 times
grades[i] = prompt("Please enter a grade. (You will be asked for 5 grades)", "");
// ask the user for a grade and store it to the array
}
for (i = 0; i < grades.length; i++) {
if (grades[i] === "" || grades[i] === null) {
invalid[invalid.length] = grades[i];
}
}
if (invalid.length !== 5) {
for (i = 0; i < grades.length; i++) {
// repeat this code the same amount of times as there are entries in the array (5)
sum += Number(grades[i]);
// add the entries together. make sure they are numbers using the Number() function
}
var average = sum / grades.length;
// divide the added entries by the number of entries (again, 5)
alert("The average of all of your numbers is: " + average);
// alert the user of the completed average
} else {
alert('You need to enter grades for this to work! Please reload the page to try again.');
}