Help with arrays and functions

gabbagabbahey38 · 12-10-2010, 04:52 AM

Hi, new to this forum but have a quick question about arrays, I've been working on this all night, and I'm at a loss. I'm trying to calculate the gpa of a user by using arrays and functions. Everything seems to be working besides two things.

The array that contains the class names (className[]) always includes an extra two variables: my sentinel value which is finish, and "undefined"
The arrays at the end won't produce a number when multiplied together. creditData[] and qualityPoints[].

Also, if you have any suggestions on my code, I'd appreciate it.

<script type="text/javascript">

</script>
</head>

<body>
<script type="text/javascript">

var promptString; /*Declares Variables*/
var className;
var numOfClasses;
var grade;
var semester;
var numCredits;
var lowerNum=1;
var upperNum=4;
var class1;
var i=0;
var counter=0;
var totalCredits=0;
var totalPoints=0;
var grade;
var counterCredits=0;
var counterGrade=0;
var points;
var gpa;
var qualityPoints;
var creditData;
var gradeData;
var x=0;
var totalQualityPoints=0;

PrintExplanation();
var className = new Array(i);
semester=prompt("Please enter the semester you would like to calculate your GPA for.");
document.write("Grade report for " + semester + "<br />");

while(class1!="finish") /*Stores the names of the classes taken into an array*/
{
class1=prompt("Enter the Class name, or finish to end");
className[i]=class1
i++
}

while(counter<=i) /*writes the classes in the array from top to bottom*/
{
document.write(className[counter] + "<br />");
counter++
}

var creditData = new Array(i)
while(counterCredits<=i) /*counts the total number of credits for all the classes*/
{
numCredits=GetValidNumberInput("How many credits is " + className[counterCredits] + " class worth?",1,4)
creditData[counterCredits]=numCredits
totalCredits=totalCredits + numCredits
counterCredits++
totalCredits=parseFloat(totalCredits);
}

var gradeData = new Array(i) /*collects information about grades in an array*/
while(counterGrade<i=)
{
points=prompt("What grade did you recieve in " + className[counterGrade] + "?");
points=ConvertGradeToPoints(points)
gradeData[counterCredits]=points
totalPoints=totalPoints+points
counterGrade++
}

while(x<=i)
{
qualityPoints=creditData[x]*gradeData[x]
totalQualityPoints=totalQualityPoints + qualityPoints
x++
}

gpa=CalculateGPA(totalCredits, qualityPoints)
document.write(gpa);

</script>
</body>

Philip M · 12-10-2010, 08:08 AM

It cannot work as you have a syntax error:-
while(counterGrade<i= )

The default of all your promts is undefined.
semester=prompt("Please enter the semester you would like to calculate your GPA for." , "" );

When you declare a variable with var you wipe out any previous instance of it:-
function ConvertGradeToPoints(grade) {
var grade;

A prompt dialog can only return a single value., that is the value entered by the user.
numCredits=GetValidNumberInput("How many credits is " + className[counterCredits] + " class worth?",1,4)
Here you have assigned "1" as the default value. The correct way is something like:-
numCredits= prompt("How many credits is " + className[counterCredits] + " class worth?","");
You must check on the validity of that value in script:-
checkValidInput(numCredits); // function checkValidInputs checks for a number within a valid range.

You have declared your array with a length of i, which has a value of 0.
var className = new Array(i);

There are probably other errors as well.

Other comments:
You have omitted the ; at the line ends in many places. It is true that the ; is not mandatory, but if you make a habit of leaving it out you will run into trouble one day.
You should place the opening brace { on the same line as the if/else/while/do/function statement, not the next line. Again, you will run into trouble if you do not follow this advice (we had a case only the other day in this forum).

Simplify your grades>points calculation:-

Code:

grade = grade.toLowerCase();
var gradeslist = ["a","b","c","d","e"]
var pointslist = [4,3,2,1,0]
for (var i =0; i<gradeslist.length; i++) {
if (gradeslist[i] == grade) {
points = pointslist[i];
}
}

Fix these errors/infelicities, try inserting some alerts at strategic positions to check on the values of your variables. If it still does not work then come back. But please see Forum Rule 1.5 re homework.

BTW, when posting here please follow the posting guidelines and wrap your code in CODE tags. This means use the octothorpe or # button on the toolbar. You can (and should) edit your previous post.

gabbagabbahey38 · 12-10-2010, 04:07 PM

Thanks for the tips. I appreciate the help, I'm not a very experienced coder, and I know my code is not up to par as far as quality goes. Thanks for the help though.