bootstrap模态框垂直居中效果

 //模态框垂直居中 function centerModals() {  $('.modal').each(    function(i) {     var $clone = $(this).clone().css('display', 'block')       .appendTo('body');     var top = Math.round(($clone.height() - $clone.find(       '.modal-content').height()) / 2);     top = top > 0 ? top : 0;     $clone.remove();     $(this).find('.modal-content').css("margin-top",       top - 50);    }); } $('.modal').on('show.bs.modal', centerModals); $(window).on('resize', centerModals);

<!--登陆弹窗--> <form action="__URL__/doLogin" method="post" class="form-horizontal">  <!--模态框声名-->  <div class="modal" id="myModal" tabindex="-1">   <!--窗口声名-->   <div class="modal-dialog modal-sm">    <!--内容声名-->    <div class="modal-content">     <div class="modal-header">      <button class="close" data-dismiss="modal">       <span>×</span>      </button>      <h4 class="modal-title">用户登录</h4>     </div>     <div class="modal-body">      <div class="form-group has-success has-feedback">       <label for="username" class="col-sm-3 control-label">账号</label>       <div class="col-sm-9">        <span class="glyphicon glyphicon-user form-control-feedback"         aria-hidden="true"></span> <span id="inputSuccess3Status"         class="sr-only">(success)</span> <input type="text"         id="username" name="username" class="form-control"         placeholder="请输入您的用户名" title="可包含中文数字和常用字符"         onkeydown="if(event.keyCode==32||event.keyCode==13){return false;}">        <!-- 禁用空格和回车 -->       </div>      </div>      <div class="form-group has-success has-feedback">       <label for="password" class="col-sm-3 control-label">密码</label>       <div class="col-sm-9">        <span class="glyphicon glyphicon-lock form-control-feedback"         aria-hidden="true"></span> <span id="inputSuccess3Status"         class="sr-only">(success)</span> <input type="password"         id="password" name="password" class="form-control"         maxlength="12" placeholder="请输入您的密码" oncopy="return false"         oncut="return false" onpaste="return false" title=""         onkeydown="if(event.keyCode==32||event.keyCode==13){return false;}">       </div>      </div>     </div>     <div class="modal-footer">      <div class="form-group">       <div class="col-sm-offset-2 col-sm-10">        <button type="submit" class="btn btn-success" id="login">现在登录         »</button>       </div>      </div>     </div>    </div>   </div>  </div> </form>