var n=prompt("Input a number: ", "Number here");
    if (n==n)
    {
      var i=1;
      do
      {
        var g=prompt("Input grade: " );

        var grade=parseInt(g);
        var total=grade+grade;
        i++;

      }
      while(i<=n);
    }
    var average=(total)/n;
    document.write("Average is: " +average);
}

var grade=parseInt(g);
 var total=grade+grade;

var grade=parseInt(g);
 total=total+grade;

var n = prompt("Input a number: ", "Number here");
while (!parseInt(n) )
{
 n=prompt("Input a number: ", "Number here");
}

var i=1;
    var total = 0;
    do
    {
        var g = prompt("Input grade: " );
        while (!parseInt(g)) {
            g = prompt("Input grade: " );
        }
        var grade = parseInt(g);
        total += grade;
        i++;

    }
    while(i<=n);
    var average=(total)/n;
    console.log("Average is: " +average);

numGrades = prompt("Enter number of grades to be entered: ");

//number of grades to be entered LOOP
for (index = 1; index <= numGrades; index++) {
  numberGrades = prompt("Enter Grade " + index);
}

//Calculation
gradePointAverage = numberGrades / numGrades;
document.write("Your GPA is " + gradePointAverage );