我需要做什么： 我需要建立一个程序，要求用户输入他们的成绩 1）任务1 - 25分 2）任务2 - 25分 3）任务3 - 25分 4）assighment4 - 25分 5）考试1 - 100分 6）期末考试 - 100分 7）最终项目--100分
所有作业的总分数为400分
不允许用户输入负分数，并且不允许他们输入超出分配可能总分限制的分数。输入所有分数后，我将分数显示为百分比和字母等级。
到目前为止有效： 该计划不接受否定，或任何高于设定的可能点数限制的等级。我无法获得“输入有效分数（0-max）”消息，因此我废弃了该功能，相反，在输入适当的值之前，程序不会向前移动。我也能够显示百分比。但是一旦你查看代码，你会看到程序实际上没有计算百分比，它只是计算（总和/总）* 100以后我做一个document.writeln我只需添加一个“％”符号。我发现这样更容易。
我无法工作： 我不能得到该死的字母等级。我知道，因为我将字母等级设置在特定范围内（例如93.9％-90％是A-），如果我这样做，我应该使用，但我不确定我是否做得对，我也设置了一个名为“字母”的变量，我试图给出A，A，B +，B，B-等值，具体取决于学生跌倒的范围。我不能让这个工作。
这是我的代码，非常感谢任何帮助。
我在这里遇到一些问题。
我可以让程序将所有等级相加并除以总数，从而得到一个百分比并在我运行程序时显示它。我似乎无法做到的是显示字母等级。
我有if语句，到目前为止，还有一个名为letter的变量，我试图将其插入到我们在代码中看到的第一个document.writeln中，但是当我尝试使用这个变量并运行程序时屏幕变白了。没有提示输入分数，没有提示，它只是白色。
我认为这与if语句的方式有关，但我不知道。
这是我的代码，一些帮助将不胜感激
<!DOCTYPE html>
<html>
<head>
<meta charset = "utf-8">
<Title>Final Grade Calculation</Title>
<script type = "text/javascript">
var assignment1;
var assignment2;
var assignment3;
var assignment4;
var exam1;
var finalexam;
var finalproject;
// the above variables represent the assignments, exams, and project.
// the following lines of code will ask the user to enter their scores. We will also try
// to make sure that the user is not entering negative numbers, or numbers above the max set of points possible for each
//assignment. Eash assignment is worth 25 points
//exams are 100
//and the final project is 100 as well, the total points possible should then be no more than 400
//before we begin to prompt the user to enter their scores we will also declare a few more variables
var a1; //assignment 1
var a2; //assignment 2
var a3; //assignment 3
var a4; //assignment 4
var e1; //exam1
var ef; //final exam
var fp; //final project
var g; //is going to be ((a1+a2+...fp)/tp)
var tp = 400; //total possible points
var letter;
//the following loops ensure that the user can only enter scores that fall withing the acceptable range for each respective assignment
//assignments have a min of 0, and a max of 25
//exam1 has a min of 0, and a max of 100
//finalexam has a min of 0 and a max of 100
//final project has a min of 0 and a max of 100
//if there is no score entered into the prompt then the variable for the respective assignment is 0 by default.
do
{
assignment1=window.prompt("Enter your score for assignment 1");
a1=parseInt(assignment1);
//window.alert("Invalid Score entered");
}
while (a1 < 0 || a1 > 25 )
if (assignment1=null)
a1=0
do
{
assignment2=window.prompt("Enter your score for assignment 2");
a2=parseInt(assignment2);
//window.alert("Invalid Score entered");
}
while (a2 < 0 || a2 > 25 )
if (assignment2=null)
a2=0
do
{
assignment3=window.prompt("Enter your score for assignment 3");
a3=parseInt(assignment3);
//window.alert("Invalid Score entered");
}
while (a3 < 0 || a3 > 25 )
if (assignment1=null)
a3=0
do
{
assignment4=window.prompt("Enter your score for assignment 4");
a4=parseInt(assignment4);
//window.alert("Invalid Score entered");
}
while (a4 < 0 || a4 > 25 )
if (assignment4=null)
a4=0
do
{
exam1=window.prompt("Enter your score for exam 1");
e1=parseInt(exam1);
//window.alert("Invalid Score entered");
}
while (e1 < 0 || e1 > 100 )
if (exam1=null)
e1=0
do
{
finalexam=window.prompt("Enter your score for the final exam");
ef=parseInt(finalexam);
//window.alert("Invalid Score entered");
}
while (ef < 0 || ef > 100 )
if (finalexam=null)
ef=0
do
{
finalproject=window.prompt("Enter your score for the final project");
fp=parseInt(finalproject);
//window.alert("Invalid Score entered");
}
while (fp < 0 || fp > 100 )
if (finalproject=null)
fp=0
// g is the variable which will be representing the final grade.
//is will give us a decimal as an answer
g = ((a1+a2+a3+a4+e1+ef+fp)/tp)*100
document.writeln("<h1>Your final score is " + g.toFixed(2) +"%</h>"); //we convert the decimal into a percentage, not really though
//the percentage displayed is only superficial, to be honest I was getting frustrated trying to find a way to make real percents
//the following if's will assign letter grades to a range of decimals.
if (g>=94)
{letter="A"}
else if (g>=93.90 || g<=90.00)
{letter="A-"}
else if (g>=89.90 || g<=87.00)
{letter="B+"}
else if (g>=86.90 || g<=84.00)
{letter="B"}
else if (g>=83.90 || g<=80.00)
{letter="B-"}
else if (g>=79.90 || g<=77.00)
{letter="C+"}
else if (g>=76.90 || g<=74.00)
{letter="C"}
else if (g>=73.90 || g<=70.00)
{letter="C-"}
else if (g>=69.90 || g<=67.00)
{letter="D+"}
else if (g>=63.90 || g<=60.00)
{letter="D-"}
else
{letter="F"};
document.writeln("<h1> Your grade is " + letter "</h1>");
</script>
</head>
</html>
答案 0 :(得分：0)
你错过了一个+来连接字符串
document.writeln("<h1> Your grade is " + letter "</h1>");
应该是
document.writeln("<h1> Your grade is " + letter + "</h1>");
除此之外它工作正常：http://jsfiddle.net/fqv9t/（document.write被小提琴警报取代）