var sortImage = fdTableSort.sortText;

function sortImagePrepareData(td, innerText) {
        var img = td.getElementsByTagName('img');
        return img.length ? img[0].src: "";
}

var sortDifficulty = fdTableSort.sortNumeric;

function sortDifficultyPrepareData(tdnode, innerText) {
    var fn = innerText.toString().toLowerCase();
    switch (fn) {
        case "easy":
            fn = 1;
            break;
        case "medium":
            fn = 2;
            break;
        case "hard":
            fn = 3;
            break;
        case "expert":
            fn = 4;
            break;
    }
    return fn;
}