Nested if/else in While loop

Question

I'm trying to make a program that determines if a grade entered is passing or failing. It stops when the user enters -1. Once the user does enter -1, it has to print out the average of the passing scores and the total amount of scores. It's not really working correctly though. What am I doing wrong?

var countTotal=0;   //variable to store total grades.
var countPassing=0; //variable to store total passing scores.
var x= 0;       //variable to contain sum of all passing scores.
var grade=parseInt(prompt("Please enter a grade."));

while (grade != (-1*1)) 
{
    if (grade > 65) {
        grade=parseInt(prompt("Please enter a grade."));
        document.write(grade + " is passing.<br>");
        x=x+grade;
        countPassing++;
    }
    else {
        grade=parseInt(prompt("Please enter a grade."));
        document.write(grade + " is failing.<br>");
    }

    countTotal++;
}

//Loop ends

document.write("Total # of grades: " + countTotal);         //Prints out total # of passing scores.
document.write("Passing average: " + ((x)/(countPassing))); //Prints out average of all passing scores.

Just to satisfy my curiousity ... what is the point of `(grade != (-1*1))`? Shouldn't `(grade != -1)` be sufficient? — Joel Etherton, Nov 14 '12 at 15:04
yeah you're absolutely right, but I just wanted to make sure that it would work as an integer. Im quite new to this haha — user1765804, Nov 14 '12 at 15:08
`document.write` is a [bad practice](http://stackoverflow.com/questions/802854/why-is-document-write-considered-a-bad-practice). — Zev Spitz, Nov 14 '12 at 15:09
@user1765804: That's quite alright, I just wanted to point it out. As a note, parseInt should take care of that for you. — Joel Etherton, Nov 14 '12 at 15:10
It's important to pass in the `radix` argument to `parseInt`: `parseInt(grade, 10)`. Otherwise, if you get something that starts with a 0, it will be interperted as octal. — Zev Spitz, Nov 14 '12 at 15:10

score 2 · Accepted Answer · answered Nov 14 '12 at 15:03

2

Try working through it by hand. The user enters the very first grade. Then the loop starts. Immediately, you ask for a new grade, discarding the first one. If you move the prompt down to the end of the loop, it should work. Like this:

while (grade != (-1*1)) 
{
    if (grade > 65) {
        document.write(grade + " is passing.<br>");
        x=x+grade;
        countPassing++;
    }
    else {
        document.write(grade + " is failing.<br>");
    }

    grade=parseInt(prompt("Please enter a grade."));
    countTotal++;
}

answered Nov 14 '12 at 15:03

Tayacan

1,836
10
15

oh ok, that makes sense. For the life of me, I could not figure out why it would do that. It actually seemed to be discarding the second value entered, but this works. Thanks. – user1765804 Nov 14 '12 at 15:10
Hmm. I tested it, and it discarded the first one. For some reason, the average was wrong too before I changed it, but it seems to work now. – Tayacan Nov 14 '12 at 15:16

Nested if/else in While loop

1 Answers1