findCoverPath(packageXml) {
    var pkg = Object(core["qs"])(packageXml, "package");
    var epubVersion = pkg.getAttribute("version"); // Try parsing cover with epub 3.
    // var node = packageXml.querySelector("item[properties='cover-image']");

    var node = Object(core["qsp"])(packageXml, "item", {
      "properties": "cover-image"
    });
    if (node) return node.getAttribute("href"); // Fallback to epub 2.

    var metaCover = Object(core["qsp"])(packageXml, "meta", {
      "name": "cover"
    });

    if (metaCover) {
      var coverId = metaCover.getAttribute("content"); // var cover = packageXml.querySelector("item[id='" + coverId + "']");

      var cover = packageXml.getElementById(coverId);
      return cover ? cover.getAttribute("href") : "";
    } else {
      return false;
    }
  }
Find the Cover Path
<item properties="cover-image" id="ci" href="cover.svg" media-type="image/svg+xml" />
Fallback for Epub 2.0
@private
@param  {node} packageXml
@return {string} href