imagesLoaded 监听 background-image 加载失败

见imagesloaded文档

<div class="js-cover-loaded" data-cover="静态图" style="background-image:url(动态图)"></div>
// 加载动图失败时尝试加载静态图
var imgLoad = imagesLoaded(".js-cover-loaded", { background: true });
imgLoad.on("always", function(){
  for ( var i = 0, len = imgLoad.images.length; i < len; i++ ) {
    var image = imgLoad.images[i];
    var $ele = $(imgLoad.elements[i]);
    $ele.removeClass("js-cover-loaded");
    if(!image.isLoaded){
      $ele.css({
        backgroundImage : "url(" + $ele.data("cover") + ")",
      });
    }
  }
});