如何通过js+css实现select的美化效果？

.div-select
{
 border: solid 1px #999;
 height: 40px;
 line-height: 40px;
 cursor: default;
}

.div-select-text
{
 float: left;
 background-color: #fff;
 height: 100%;
 word-break: keep-all;
 overflow: hidden;
 cursor: default;
}

 .div-select-text > div
 {
  padding: 3px;
  line-height: 34px;
 }

.div-select-arrow
{
 background-color: #fff;
 float: right;
 width: 40px;
 height: 100%;
 color: #999;
 cursor: default;
}

 .div-select-arrow > div
 {
  border: solid 1px #999;
  margin: 2px;
  height: 34px;
  background-color: #f2f2f2;
  text-align: center;
  line-height: 34px;
  font-size: 22px;
 }

.div-select-list
{
 position: absolute;
 float: left;
 top: 100px;
 left: 100px;
 border: solid 1px #999;
 max-height: 300px;
 overflow: auto;
 background-color: #9f9;
 display: none;
 z-index: 9100;
}

 .div-select-list .div-select-item:nth-child(2n+1)
 {
  background-color: #fff;
 }

.div-select-item
{
 height: 50px;
 line-height: 50px;
 padding-left: 3px;
 padding-right: 3px;
 background-color: #f2f2f2;
 word-break: keep-all;
 overflow: hidden;
 cursor: default;
}

.div-select-item-hover
{
 background-color: #3399ff!important;
}

.div-select-selected
{
 background-color: #3399ff !important;
}

//select美化
var divSelectListIndex = 0;

$(function () {
 initDivSelect();
});

//初始化select美化插件
function initDivSelect() {
 $(".div-select-target").each(function () {
  divSelectListIndex++;
  var select = $(this);

  if (select.css("display") == "none") {
   return;
  }
  else {
   select.css("display", "none")
  }

  if (select.next("div").find(".div-select-list").length == 0) {
   select.after('<div><div class="div-select"><div class="div-select-text"><div></div></div><div class="div-select-arrow"><div>∨</div></div></div></div>');
   $("body").append('<div class="div-select-list div-select-list-' + divSelectListIndex + '"></div>');
  }

  var div = select.next("div");
  var divText = div.find(".div-select-text");
  var divSelect = div.find(".div-select");
  var divArrow = div.find(".div-select-arrow");
  var list = $(".div-select-list-" + divSelectListIndex);

  function updateText(item) {
   divText.find("div").html(item.html());
  }

  select.find("option").each(function () {
   var option = $(this);
   var text = option.html();
   var value = option.attr("value");
   list.append('<div class="div-select-item" value="' + value + '">' + text + '</div>');
   list.find(".div-select-item:last").click(function () {
    var item = $(this);
    var value = item.attr("value");
    select.val(value);
    select.change();
    list.find(".div-select-selected").removeClass("div-select-selected");
    item.addClass("div-select-selected");
    updateText(item);
    list.hide();
   });

   list.find(".div-select-item:last").mouseenter(function () {
    var item = $(this);
    var selectedMark = list.find(".div-select-selected");
    selectedMark.removeClass("div-select-selected");
    selectedMark.addClass("div-select-selected-mark");
    list.find(".div-select-item-hover").removeClass("div-select-item-hover");
    item.addClass("div-select-item-hover");
    updateText(item);
   });
  });

  list.mouseleave(function () {
   var selectedMark = list.find(".div-select-selected-mark");
   if (list.find(".div-select-selected").length == 0) {
    selectedMark.addClass("div-select-selected");
    updateText(selectedMark);
   }
   selectedMark.removeClass("div-select-selected-mark");
   list.find(".div-select-item-hover").removeClass("div-select-item-hover");
  });

  if (select.attr("width")) {
   divSelect.width(select.attr("width") - 2);
   divText.width(divSelect.width() - divArrow.width());
   if (select.attr("width") > list.width()) {
    list.width(divSelect.width());
   }
  }

  div.keydown(function (e) {
   list.find(".div-select-selected-mark").removeClass("div-select-selected-mark");
   list.find(".div-select-item-hover").addClass("div-select-selected");
   list.find(".div-select-item-hover").removeClass("div-select-item-hover");
   if (e.keyCode == 40) {
    var currentSelected = list.find(".div-select-selected");
    var nextSelected = currentSelected.next(".div-select-item");
    if (nextSelected.length == 0) {
     nextSelected = list.find(".div-select-item:first");
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     list.scrollTop(0);
    } else {
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     var i = 0;
     while (nextSelected.position().top < 0
      || nextSelected.position().top > list.height() - nextSelected.height()) {
      list.scrollTop(list.scrollTop() + nextSelected.height());
      if (i++ > 100) break;
     }
    }
    updateText(nextSelected);
    return false;
   }
   if (e.keyCode == 38) {
    var currentSelected = list.find(".div-select-selected");
    var nextSelected = currentSelected.prev(".div-select-item");
    if (nextSelected.length == 0) {
     nextSelected = list.find(".div-select-item:last");
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     list.scrollTop(list.find(".div-select-item").length * nextSelected.height());
    }
    else {
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     var i = 0;
     while (nextSelected.position().top < 0
      || nextSelected.position().top > list.height() - nextSelected.height()) {
      list.scrollTop(list.scrollTop() - nextSelected.height());
      if (i++ > 100) break;
     }
    }
    updateText(nextSelected);
    return false;
   }
   if (e.keyCode == 13) {
    var selectedItem = list.find(".div-select-selected");
    var value = selectedItem.attr("value");
    select.val(value);
    list.hide();
    select.change();
   }
  });

  divSelect.click(function () {
   $("a").bind("click", function () {
    $("a").unbind("click");
    list.hide();
   });

   if (list.css("display") == "none") {
    list.show();
   }
   else {
    list.hide();
   }

   list.css("top", divSelect.offset().top + divSelect.height() + 1);
   list.css("left", divSelect.offset().left);
   if ($(window).scrollTop() + $(window).height() < list.offset().top + list.height() + 2) {
    list.css("top", $(window).scrollTop() + $(window).height() - list.height() - 2);
   }
   if (list.width() < divSelect.width()) {
    list.width(divSelect.width());
   }

   var currentSelected = list.find(".div-select-selected");
   if (currentSelected.position().top > list.height() - currentSelected.height()) {
    list.scrollTop(currentSelected.position().top - currentSelected.height() * 2);
   }
   return false;
  });

  $("html,body").bind("click", function () {
   list.hide();
  });
  list.click(function () {
   return false;
  });

  function initSelect() {
   list.find(".div-select-selected").removeClass("div-select-selected");
   var matchItem = list.find(".div-select-item[value='" + select.val() + "']");
   if (matchItem.length > 0) {
    matchItem.addClass("div-select-selected");
    updateText(matchItem);
   }
  }
  initSelect();
  select.change(function () {
   initSelect();
  });
 }); // $(".div-select-target").each
}

<link type="text/css" href="~/Scripts/DivSelect/divSelect.css" rel="stylesheet" />
<script type="text/javascript" src="~/Scripts/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="~/Scripts/DivSelect/divSelect.js"></script>

<link type="text/css" href="~/Scripts/DivSelect/divSelect.css" rel="stylesheet" />
<script type="text/javascript" src="~/Scripts/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="~/Scripts/DivSelect/divSelect.js"></script>

<div style="border: solid 1px #f99; margin: 50px; padding: 50px;">
 <select name="sel" class="div-select-target" width="200" >
  <option value="1">中国</option>
  <option value="2">美国</option>
  <option value="3">法国</option>
  <option value="4">英国</option>
  <option value="5">俄罗斯</option>
  <option value="6">德国</option>
  <option value="7">韩国</option>
  <option value="8">日本</option>
  <option value="9">印度</option>
  <option value="10">巴西</option>
  <option value="11">意大利</option>
  <option value="12">这个国家的名称很长很长很长很长很长很长很长很长</option>
  <option value="13">瑞士</option>
  <option value="14">越南</option>
  <option value="15">缅甸</option>
  <option value="16">泰国</option>
  <option value="17">加拿大</option>
  <option value="18" selected="selected">南非</option>
  <option value="19">澳大利亚</option>
  <option value="20">新西兰</option>
  <option value="21">挪威</option>
  <option value="22">巴勒斯坦</option>
  <option value="23">以色列</option>
  <option value="24">新加坡</option>
  <option value="25">马来西亚</option>
  <option value="26">波兰</option>
  <option value="27">国家27</option>
  <option value="28">国家28</option>
  <option value="29">国家29</option>
  <option value="30">国家30</option>
  <option value="31">国家31</option>
  <option value="32">国家32</option>
  <option value="33">国家33</option>
  <option value="34">国家34</option>
  <option value="35">国家35</option>
  <option value="36">国家36</option>
  <option value="37">国家37</option>
  <option value="38">国家38</option>
 </select>
</div>
<div style="border: solid 1px #f99; margin: 50px; padding: 50px; margin-top: 700px; margin-bottom: 700px;">
 <select name="sel" class="div-select-target" width="200" >
  <option value="1">中国</option>
  <option value="2">美国</option>
  <option value="3">法国</option>
  <option value="4">英国</option>
  <option value="5">俄罗斯</option>
  <option value="6" selected="selected">德国</option>
  <option value="7">韩国</option>
  <option value="8">日本</option>
 </select>
</div>

.div-select
{
 border: solid 1px #999;
 height: 40px;
 line-height: 40px;
 cursor: default;
}

.div-select-text
{
 float: left;
 background-color: #fff;
 height: 100%;
 word-break: keep-all;
 overflow: hidden;
 cursor: default;
 font-size: 16px;
 font-family: 微软雅黑,雅黑;
}

 .div-select-text > div
 {
  padding: 3px;
  line-height: 34px;
 }

.div-select-arrow
{
 background-color: #fff;
 float: right;
 width: 40px;
 height: 100%;
 color: #999;
 cursor: default;
}

 .div-select-arrow > div
 {
  border: solid 1px #999;
  margin: 2px;
  height: 34px;
  background-color: #f2f2f2;
  text-align: center;
  line-height: 34px;
  font-size: 22px;
 }

.div-select-list
{
 position: absolute;
 float: left;
 top: 100px;
 left: 100px;
 border: solid 1px #999;
 max-height: 300px;
 overflow: hidden;
 background-color: #9f9;
 display: none;
 z-index: 9100;
 font-size: 16px;
 font-family: 微软雅黑,雅黑;
}

 .div-select-list .div-select-item:nth-child(2n+1)
 {
  background-color: #fff;
 }

.div-select-item
{
 height: 50px;
 line-height: 50px;
 padding-left: 3px;
 padding-right: 3px;
 background-color: #f2f2f2;
 word-break: keep-all;
 overflow: hidden;
 cursor: default;
}

.div-select-item-hover
{
 background-color: #3399ff!important;
}

.div-select-selected
{
 background-color: #3399ff !important;
}

.div-select-list-scrollbar
{
 position: absolute;
 float: left;
 border: solid 1px #999;
 border-left: 0;
 background-color: #e8e8ec;
 width: 40px;
 height: 300px;
 display: none;
 cursor: default;
 z-index: 9101;
}

.div-select-scrollbar-up
{
 border-bottom: solid 1px #fff;
 height: 39px;
 font-size: 22px;
 line-height: 39px;
 color: #999;
 background-color: #cdcdcd;
 text-align: center;
}

.div-select-scrollbar-pos
{
 height: 220px;
}

 .div-select-scrollbar-pos > div:last-child
 {
  width: 40px;
  height: 20px;
  background-color: #cdcdcd;
 }

.div-select-scrollbar-down
{
 border-top: solid 1px #fff;
 height: 39px;
 font-size: 22px;
 line-height: 39px;
 color: #999;
 background-color: #cdcdcd;
 text-align: center;
}

//select美化
var divSelectListIndex = 0;

$(function () {
 initDivSelect();
});

//初始化select美化插件
function initDivSelect() {
 $(".div-select-target").each(function () {
  divSelectListIndex++;
  var select = $(this);

  if (select.css("display") == "none") {
   return;
  }
  else {
   select.css("display", "none")
  }

  if (select.next("div").find(".div-select-list").length == 0) {
   select.after('<div><div class="div-select"><div class="div-select-text"><div></div></div><div class="div-select-arrow"><div>∨</div></div></div></div>');
   $("body").append('<div class="div-select-list div-select-list-' + divSelectListIndex + '"></div>');
  }

  var div = select.next("div");
  var divText = div.find(".div-select-text");
  var divSelect = div.find(".div-select");
  var divArrow = div.find(".div-select-arrow");
  var list = $(".div-select-list-" + divSelectListIndex);
  var scrollbar;
  var scrollbarPosTop;
  var scrollbarPos;
  var scrollbarScrollHeight;
  var scrollbarUp;
  var scrollbarDown;
  var itemHeight;
  var itemCount;
  var itemsHeight;
  var scrollFlag = false;

  function updateText(item) {
   divText.find("div").html(item.html());
  }

  select.find("option").each(function () {
   var option = $(this);
   var text = option.html();
   var value = option.attr("value");
   list.append('<div class="div-select-item" value="' + value + '">' + text + '</div>');
   list.find(".div-select-item:last").click(function () {
    var item = $(this);
    var value = item.attr("value");
    select.val(value);
    select.change();
    list.find(".div-select-selected").removeClass("div-select-selected");
    item.addClass("div-select-selected");
    updateText(item);
    list.hide();
    if (scrollbar) scrollbar.hide();
   });

   list.find(".div-select-item:last").mouseenter(function () {
    var item = $(this);
    var selectedMark = list.find(".div-select-selected");
    selectedMark.removeClass("div-select-selected");
    selectedMark.addClass("div-select-selected-mark");
    list.find(".div-select-item-hover").removeClass("div-select-item-hover");
    item.addClass("div-select-item-hover");
    updateText(item);
   });
  });

  list.mouseleave(function () {
   var selectedMark = list.find(".div-select-selected-mark");
   if (list.find(".div-select-selected").length == 0) {
    selectedMark.addClass("div-select-selected");
    updateText(selectedMark);
   }
   selectedMark.removeClass("div-select-selected-mark");
   list.find(".div-select-item-hover").removeClass("div-select-item-hover");
  });

  if (select.attr("width")) {
   divSelect.width(select.attr("width") - 2);
   divText.width(divSelect.width() - divArrow.width());
  }
  else {
   divText.width(list.width());
  }

  div.keydown(function (e) {
   list.find(".div-select-selected-mark").removeClass("div-select-selected-mark");
   list.find(".div-select-item-hover").addClass("div-select-selected");
   list.find(".div-select-item-hover").removeClass("div-select-item-hover");
   if (e.keyCode == 40) {
    var currentSelected = list.find(".div-select-selected");
    var nextSelected = currentSelected.next(".div-select-item");
    if (nextSelected.length == 0) {
     nextSelected = list.find(".div-select-item:first");
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     list.scrollTop(0);
    } else {
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     var i = 0;
     while (nextSelected.position().top < 0
      || nextSelected.position().top > list.height() - nextSelected.height()) {
      list.scrollTop(list.scrollTop() + nextSelected.height());
      if (i++ > 100) break;
     }
    }
    updateText(nextSelected);
    updateScrollbarPos();
    return false;
   }
   if (e.keyCode == 38) {
    var currentSelected = list.find(".div-select-selected");
    var nextSelected = currentSelected.prev(".div-select-item");
    if (nextSelected.length == 0) {
     nextSelected = list.find(".div-select-item:last");
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     list.scrollTop(list.find(".div-select-item").length * nextSelected.height());
    }
    else {
     nextSelected.addClass("div-select-selected");
     currentSelected.removeClass("div-select-selected");
     var i = 0;
     while (nextSelected.position().top < 0
      || nextSelected.position().top > list.height() - nextSelected.height()) {
      list.scrollTop(list.scrollTop() - nextSelected.height());
      if (i++ > 100) break;
     }
    }
    updateText(nextSelected);
    updateScrollbarPos();
    return false;
   }
   if (e.keyCode == 13) {
    var selectedItem = list.find(".div-select-selected");
    var value = selectedItem.attr("value");
    select.val(value);
    list.hide();
    if (scrollbar) scrollbar.hide();
    select.change();
   }
  });

  itemHeight = list.find(".div-select-item:first").height();
  itemCount = list.find(".div-select-item").length;
  itemsHeight = itemHeight * itemCount;
  if (itemsHeight > list.height()) {
   $("body").append('<div class="div-select-list-scrollbar div-select-list-scrollbar-' + divSelectListIndex + '"><div class="div-select-scrollbar-up">∧</div><div class="div-select-scrollbar-pos"><div></div><div></div></div><div class="div-select-scrollbar-down">∨</div></div>');
  }
  scrollbar = $(".div-select-list-scrollbar-" + divSelectListIndex);
  scrollbarPosTop = scrollbar.find(".div-select-scrollbar-pos").find("div:first");
  scrollbarPos = scrollbar.find(".div-select-scrollbar-pos").find("div:last");
  scrollbarScrollHeight = scrollbarPos.parent().height() - scrollbarPos.height();
  scrollbarUp = scrollbar.find(".div-select-scrollbar-up");
  scrollbarDown = scrollbar.find(".div-select-scrollbar-down");
  scrollbar.click(function () {
   return false;
  });
  scrollbarUp.click(function () {
   list.scrollTop(list.scrollTop() - list.height());
   updateScrollbarPos();
  });
  scrollbarDown.click(function () {
   list.scrollTop(list.scrollTop() + list.height());
   updateScrollbarPos();
  });
  scrollbar.mousedown(function () {
   scrollFlag = true;
  });
  scrollbar.mouseup(function () {
   scrollFlag = false;
  });
  scrollbar.mousemove(function (e) {
   if (scrollFlag) {
    var pos = e.pageY - scrollbar.offset().top - 50;
    if (pos <= scrollbarScrollHeight) {
     scrollbarPosTop.height(pos);
     list.scrollTop(scrollbarPosTop.height() / scrollbarScrollHeight * (itemsHeight - list.height()));
    }
   }
  });

  function updateScrollbarPos() {
   scrollbarPosTop.height(scrollbarScrollHeight * list.scrollTop() * 1.0 / (itemsHeight - list.height()));
   if (list.scrollTop() + list.height() == itemsHeight) {
    scrollbarPosTop.height(scrollbarScrollHeight);
   }
  }

  divSelect.click(function () {
   $("a").bind("click", function () {
    $("a").unbind("click");
    list.hide();
    scrollbar.hide();
   });

   if (list.css("display") == "none") {
    list.show();
    scrollbar.show();
   }
   else {
    list.hide();
    scrollbar.hide();
   }

   list.css("top", divSelect.offset().top + divSelect.height() + 1);
   list.css("left", divSelect.offset().left);
   var listOffsetTop = list.offset().top;
   if ($(window).scrollTop() + $(window).height() < list.offset().top + list.height() + 2) {
    list.css("top", $(window).scrollTop() + $(window).height() - list.height() - 2);
   }
   if (list.width() < divSelect.width()) {
    if (!(itemsHeight > list.height())) {
     list.width(divSelect.width());
    }
    else {
     list.width(divSelect.width() - scrollbar.width());
    }
   }

   scrollbar.find(".div-select-scrollbar-pos").find("div:first").height(0);
   scrollbar.css("left", divSelect.offset().left + list.width() + 1);
   scrollbar.css("top", divSelect.offset().top + divSelect.height() + 1);
   if ($(window).scrollTop() + $(window).height() < listOffsetTop + list.height() + 2) {
    scrollbar.css("top", $(window).scrollTop() + $(window).height() - list.height() - 2);
   }

   var currentSelected = list.find(".div-select-selected");
   if (currentSelected.position().top > list.height() - currentSelected.height()) {
    list.scrollTop(currentSelected.position().top - currentSelected.height() * 2);
   }
   updateScrollbarPos();

   return false;
  });

  $("html,body").bind("click", function () {
   list.hide();
   scrollbar.hide();
  });
  list.click(function () {
   return false;
  });

  function initSelect() {
   list.find(".div-select-selected").removeClass("div-select-selected");
   var matchItem = list.find(".div-select-item[value='" + select.val() + "']");
   if (matchItem.length > 0) {
    matchItem.addClass("div-select-selected");
    updateText(matchItem);
   }
  }
  initSelect();
  select.change(function () {
   initSelect();
  });
 }); // $(".div-select-target").each
}