在While循环中嵌套if / else

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.

Answer 1

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++;
}