javascript - 如何计算平均成绩

Question

我是 JavaScript 的新手，似乎无法弄清楚为什么我的最后一个函数没有做它应该做的事情，即使用用户输入的成绩(数字)的平均值来返回字母成绩。

我的第一个函数正常工作，我的第二个函数编写正确(我认为)但是对于我的第三个函数我不确定我做错了什么，因为当我测试运行时没有任何显示。

这是我在代码中所做的:

var grades = [];
var totalSum = 0;


function myFunction() {
  for (var i = 0; i < 5; i++) {
    grades[i] = parseInt(prompt("Enter a Grade: "));
    document.getElementById("gradeInput").innerHTML += grades[i] + "  ";
  }
}


function gradeAverage() {
  for (var i = 0; i < grades.length; i++) {
    totalSum += grades[i];
    var average = totalSum / grades.length;
  }
}


function letterGrade() {

  if (totalSum <= 90) {
    document.getElementById("finalGrade").innerHTML += average + " A";
  } else if (totalSum <= 80) {
    document.getElementById("finalGrade").innerHTML += average + " B";
  } else if (totalSum <= 70) {
    document.getElementById("finalGrade").innerHTML += average + " C";
  } else if (totalSum <= 60) {
    document.getElementById("finalGrade").innerHTML += average + " D";
  } else {
    document.getElementById("finalGrade").innerHTML += average + " F";
  }
}

myFunction();
gradeAverage();
letterGrade();

Answer 1

你需要将 average 变量作为全局变量，并像这样在你的 letterGrade() 中进行一些修复:

添加:如果分数为 90 或以下，letterGrade() 将始终返回 A

var grades = [];
var totalSum = 0;
var average = 0

// function to read five values from series of prompts stored in array
function myFunction() {
  for (var i = 0; i < 5; i++) {
    grades[i] = parseInt(prompt("Enter a Grade: "));
    document.getElementById("gradeInput").innerHTML += grades[i] + "  ";
  }
}

// function to calculate the average of the five entered grades and store it in a variable
function gradeAverage() {
  for (var i = 0; i < grades.length; i++) {
    totalSum += grades[i];
    average = totalSum / grades.length;
  }
}

// funtion to use the average of entered grades to determine letter grade that it will return to the user
function letterGrade() {

  if (average >= 90 && average <= 100) {
    document.getElementById("finalGrade").innerHTML += average + " A";
  } else if (average >= 80 && average <= 89) {
    document.getElementById("finalGrade").innerHTML += average + " B";
  } else if (average >= 70 && average <= 79) {
    document.getElementById("finalGrade").innerHTML += average + " C";
  } else if (average >= 60 && average <= 69) {
    document.getElementById("finalGrade").innerHTML += average + " D";
  } else if (average <= 59) {
    document.getElementById("finalGrade").innerHTML += average + " F";
  }
}

myFunction();
gradeAverage();
letterGrade();

<p id="gradeInput">You entered the following grades: </p>
<p id="finalGrade">Your grade average is: </p>