判断滚动条滚到底部

原理：文档高度 = 视口高度 + 滚动条高度

1.若是一整个浏览窗口的滚动条：

$(window).scroll(function () {
    var documentHeight = $(document).height();//1188
    var windowHeight = $(window).height();//706
    var scrollTop = $(document).scrollTop();//482
    var sh = windowHeight + scrollTop ;
    console.log("sh="+sh+"documentHeight="+documentHeight);

    if(windowHeight+scrollTop ==  documentHeight){
                //滚动到底部
    }

});
或者
$(document).scroll(function () {
    var documentHeight = $(document).height();//1188
    var windowHeight = $(window).height();//706
    var scrollTop = $(document).scrollTop();//482
    var sh = windowHeight + scrollTop ;
    console.log("sh="+sh+"documentHeight="+documentHeight);

    if(windowHeight+scrollTop ==  documentHeight){
                //滚动到底部
    }

});
2.若是某个div的滚动条：

$(document).ready(function () {
    $(".tongModalBox").scroll(function () {
        var documentHeight = $(this).prop('scrollHeight');//或$(this)[0].scrollHeight
        var windowHeight = $(this).height();
        var scrollTop = $(this).scrollTop();
        var sh = windowHeight + scrollTop ;
        console.log("sh="+sh+"documentHeight="+documentHeight);

        if(windowHeight+scrollTop ==  documentHeight){
                //滚动到底部
        }

    });
});