在JS事件里面怎么写CSS样式,修改下拉框选项的背景色,Js如下setTimeout(function(){ $(".fr-trigger-text.fr-border-box").css({"background":"rgba(0,0,0,0)"});$(".fr-trigger-text").find("input").css({"background":"rgba(0,0,0,0)","color":"#c0c0c0"}); $(".fr-trigger-text").css("border","none"); $(".fr-trigger-btn-up").css({"background":"rgba(0,0,0,0)","border":"none"});$(".fr-combo-list").css({"background-color":"black"});},200) 设置成黑色没反应