原生CSS设置预加载图片之前的默认背景图

/*默认加载图片*/.class-name { /*背景图片*/background: url(../../img/banner/banner-default.jpg) no-repeat center bottom;width: 100%;height: 861px;}.class-name:after { /*默认加载背景图*/position: absolute;content: url(../../img/banner/banner-default.jpg);z-index: -1;}