Try to calculate gpa in gdut website (algorithm is wrong)

gpa.js

var listhead = $$(".datelisthead");
var sumScoreRank = 0;
var sumPoint = 0;

for (var i = listhead.nextSibling; i.nodeName == "TR"; i = i.nextSibling) {
    var score = parseFloat(i.childNodes[4].innerHTML);
    var point = parseFloat(i.childNodes[8].innerHTML);
    if (isNaN(score)) continue;
    sumScoreRank += score * scoreToRank(score);
    sumPoint += point;
}

var gpa = (sumScoreRank * 4) / (sumPoint * 100);

function scoreToRank(score) {
    var rank = 0;
    switch (parseInt(score / 10)) {
    case 10:
	return 4;
    case 9:
	return 4;
    case 8:
	return 3;
    case 7:
	return 2;
    case 6:
	return 1;
    default:
	return 0;
    }
}