帮我完善这个拼图游戏的js代码直接给出完善后的代码不需要解释var aDivID = null;var aDivClass = null; var Flag = 0;function change aDiv alertaDiv; if!Flag aDivID = aDiv; aDivClass = documentgetElementByIdaDivclassName; Flag = 1;

var aDivID = null; var aDivClass = null; var Flag = 0; var puzzleSize = 4; // 拼图大小，4x4 var emptyIndex = puzzleSize * puzzleSize - 1; // 空白块的索引

function change(aDiv) { var div = document.getElementById(aDiv); var divIndex = parseInt(div.getAttribute('data-index'));

if (!Flag) {
    // 选中第一个块
    aDivID = aDiv;
    aDivClass = div.className;
    Flag = 1;
} else if (divIndex == emptyIndex) {
    // 点击了空白块，交换两个块的样式和数据
    var emptyDiv = document.querySelector('.spacediv');
    div.className = emptyDiv.className;
    emptyDiv.className = aDivClass;
    emptyDiv.innerHTML = div.innerHTML;
    div.innerHTML = '';
    emptyIndex = divIndex;
    Flag = 0;
} else {
    // 取消选中
    aDivID = null;
    aDivClass = null;
    Flag = 0;
}

}