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执行应该做的事情，即使用用户输入的平均分数（数字）返回字母分数。

我的第一个函数正在工作，我的第二个函数正确编写（我认为），但是对于我的第三个函数，我不确定自己做错了什么，因为当我测试运行时，什么都没有显示。

这是我在代码中所做的事情：

Failed to activate protocol version: "CMAKE_HOME_DIRECTORY" is set but incompatible with configured source directory value

Answer 1

在提供解决方案之前，您需要了解javascript中变量的范围。

考虑以下代码：

function myFunction() {
    var carName = "Volvo";
    //code here CAN use the variable carName
}

function someAnotherFunction(){
    console.log(carName);
    //code here CANNOT use the variable carName
    //It will the error that carName is not defined.
}
//code here CANNOT use the variable carName

另一种情况：

var carName = "Volvo";
function myFunction() {
    console.log(carName);
    //code here CAN use the variable carName
}

function someAnotherFunction(){
    console.log(carName);
    //code here CAN use the variable carName
}
console.log('Check my value here again: '+carName);
//code here CAN also use the variable carName

此处要注意的区别是，变量的范围/可见性仅限于放置该变量的左括号和右括号。在右方括号外，声明该括号的变量将在括号外不可见。

以同样的方式，您不能在声明位置的方括号外使用 average 变量。

看看您的代码，几件事需要更改。

将平均声明移到方括号之外，以使其可见。

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

在计算成绩的函数中，需要添加平均值大于90的条件。

function letterGrade() {

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

休息就可以了。

希望这会有所帮助。

Answer 2

您需要将平均变量设置为全局变量，并在letterGrade（）中进行如下修复：

添加：如果得分为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>

Answer 3

将平均var声明移到函数外部（不推荐使用，请参阅后面）
将ifs从<=反转为> =
在if中使用平均值而不是总和

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

最好通过var：

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

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

// funtion to use the average of entered grades to determine letter grade that it will return to the user
function letterGrade(grades) {
  var totalSum = getSum(grades);
  var average = totalSum / grades.length;
  var finalGrade = "";
  if (average >= 90) {
    finalGrade = "A";
  } else if (average >= 80) {
    finalGrade = "B";
  } else if (average >= 70) {
    finalGrade = "C";
  } else if (average >= 60) {
    finalGrade = "D";
  } else {
    finalGrade = "F";
  }
  document.getElementById("finalGrade").innerHTML += average + " " + finalGrade;
}

var grades = getGrades()
letterGrade(grades);

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

Answer 4

这是一个范围问题。您需要在顶部而不是在函数average内定义变量gradeAverage。

var grades = [];
var totalSum = 0;
var average = 0; /* Added */

// 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 (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();

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

Answer 5

这里有3个问题：

在第三个函数中，尽管未全局定义它，但仍使用“ average”事件-这意味着该事件在函数中不可用。
似乎您检查了totalSum <= x，即使您可能想检查平均值<= x。

第3个功能中的检查顺序始终会导致第一个检查。因为即使平均<= 60也等于<90。颠倒检查顺序，因此较低的成绩将是第一名：

if (totalSum <= 50) {
    document.getElementById("finalGrade").innerHTML += average + " F";
} else if(totalSum <= 60) {
    document.getElementById("finalGrade").innerHTML += average + " D";
} else if (totalSum <= 70) {
    document.getElementById("finalGrade").innerHTML += average + " C";
} else if (totalSum <= 80) {
    document.getElementById("finalGrade").innerHTML += average + " B";
} else if (totalSum <= 90) {
    document.getElementById("finalGrade").innerHTML += average + " A";
} else {
    document.getElementById("finalGrade").innerHTML += average + " A+";
}

如何计算平均成绩

5 个答案: