代码如下：加载结束事件 

$('.fr-trigger-btn-up').css('background-color', '#fff'); //下拉处背景色
$('.fr-trigger-center').css("background", "url('/webroot/pic/sanjiao.png')center center / 150%                                                      250% no-repeat");//下拉框按钮   
$('.fr-date-trigger-center').css("background","url('/webroot/pic/rli1.png')center center / 100%                                                    100% no-repeat");//日历框按钮