Adding an array and converting letters to numbers - how do i?

[boimonster]

This is what I want to be able to do: I want to add the total credit hours the user inputs and display it. As you notice, it loops, but how do I add the course[Info][2] values to each other?
Also, how do I convert the letter grade (course[Info][1]) values into numbers and use it in a function to calculate GPA?

This is what I have so far:

var userName = prompt("Please enter your name.");
var course = new Array();
var Info = 0;

do
{

course[Info] = new Array();
course[Info][0] = prompt("What is the class name?");
course[Info][1] = prompt("What is your letter grade?");
course[Info][2] = prompt("How many credit hours was the class worth?");

Info++;

var courseAdd = prompt("Do you wish to add more classes?");
} while (courseAdd == "yes" || courseAdd == "Yes");

var numCourse = 0;

document.write("<H2 align='center'>" + userName + "'s GPA</H2><br>");
document.write("<table bgcolor='yellow' align='center' border='1' cellpadding='4' width='75%'>");
document.write("<tr>");
document.write("<td>Course</td><td align='center'>Course Grade</td><td align='center'>Course Hours</td>");
document.write("</tr>");

while (numCourse < Info)
{
document.write("<tr>");
document.write("<td>");
document.write (course[numCourse][0]);
document.write("</td>");
document.write("<td align='center'>");
document.write (course[numCourse][1]);
document.write("</td>");
document.write("<td align='center'>");
document.write (course[numCourse][2]);
document.write("</td>");
document.write("</tr>");

// increment the counter
numCourse++;
}

[Kor]

It looks like you know some other language, but new in javascript. Let's see, at a first glance:

1. no need to do to fire code lines. You may insert those code lines in to a function

function blahblah(parameters_optional){
..
..
}

... and fire this function when an event occures (onload, onclick, onmouseover.... and so on)

2. document.write is a weak function, it will not change dinamically the content. It will work, yes, in your case and if a single input, yet...

3. while ((courseAdd == "yes") || (courseAdd == "Yes")){
..
..
}

or better:

while (courseAdd.toLowerCase() == "yes"){
..
..
}

in fact, as you have no loop to modify the "yes" parameter, the if condition it looks proper to me:

if (courseAdd.toLowerCase() == "yes"){
..
..
}
else{...}

while will do a loop each time, decreasing the code speed...

3. to parse a string into an integer use parseInt()

parseInt(s,b) s=string; b=num. base (default b=10)

It will return an number if the string begin with a number, but till first character other than a number:

parseInt('12a9') = 12;
parseInt('12.09') = 12;
parseInt('a12') = NaN;