scrollTop无法在使用jQuery的示例上工作？

Question

您能告诉我为什么scrollTop无法正常工作。 实际上，我想在给出命令以在其前面添加文字的同时滚动关注该焦点。 实际上，焦点位于文本前面的文本顶部。 我需要重点应该保持静止。

这是我的小提琴http://jsfiddle.net/d9584/21/

当我在前面添加文字时，焦点会移到行首。

$("#contend").scroll(function () {
    if ($(this).scrollTop() === 0) {
        alert("ssss");
        $("#pre").prepend(" Distinguished service of a high degree to Australia or to humanity at largefjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda  sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda  sdflkjsdlfjsldfj sdfsjdflsf adasda  sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf sdfjsflsj sdflkjsdlfjsldfj sdfsjdflsf adasda");
        alert($("#pre")[0].scrollHeight)
        $("#pre").prependTo("#contend");
        document.getElementById("content").scrollTop = $("#pre")[0].scrollHeight
    }
});

$("#contend").scroll(function () {
    if ($('#contend').scrollTop() >= $('#contend')[0].scrollHeight - document.body.offsetHeight) {
        $("#pre").html('');
    }
});

Answer 1

我认为

$(this).scrollTop() 

永远不会为0

尝试改变

if ($(this).scrollTop() === 0) {

至

if( $(this).scrollTop() < 1) {