求dropdowm 下拉框组件的完整用法

<div class="dropdown">

            <button class="btn btn-default dropdown-toggle" type="button" id="myDropdown" data-toggle="dropdown" aria-expanded="true">

                保密

                <span class="caret"></span>

            </button>

            <ul class="dropdown-menu" role="menu" aria-labelledby="myDropdown">

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">保密</a></li>

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">男</a></li>

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">女</a></li>

            </ul>

        </div>

$(document).ready(function () {



        $(".dropdown-menu li a").bind("click", function () {

            var $this = $(this);

            var $a = $this.parent().parent().prev()

            $a.text($this.text());

            $a.append("<span class='caret'>");

            $("#UserSex").val($this.index());

        });

        var sex = $("#UserSex").val();//这个是个隐藏控件，用来记录当前选择的性别

        $(".dropdown-menu li a").eq(sex).click();

    });