绑定scroll事件 滚动条到达底部时 解除scroll事件 ajax加载数据 如果数据没全部载入 再次绑定scroll事件

$(document).ready(function() {
    $(window).bind("scroll", GetData);

    function GetData() {
        var windowHeight = $(window).height();
        var scrollHeight = $(document).scrollTop();
        var screenBottom = windowHeight + scrollHeight;
        var documentHeight = $(document).height();
        if (screenBottom >= documentHeight) {
            $(window).unbind();
            $.ajax({
                type: "post",
                url: "GetData.aspx",
                data: "action=data",
                success: function(data) {
                    data = eval("(" + data + ")");
                    if (data.ret = 1) {
                        var html = "";
                        for (var i = 0; i < 12; i++) {
                            html += ‘<div style=" border:1px solid; width:198px; float:left; height:200px" >‘ + i + ‘</div>‘;
                        }
                        $("#div_main").append(html);
                        $(window).bind("scroll", GetData);
                    }
                }
            })

        }
    }
});