function tocIsNcx() {

            var tocItem = getTocItem();
            var contentDocURI = tocItem.href;
            var fileExtension = contentDocURI.substr(contentDocURI.lastIndexOf('.') + 1);

            return fileExtension.trim().toLowerCase() === "ncx";
        }
Get spine item data in readium-shared-js accepted format.
@param spineIndex the index of the item within the spine
@returns Spine item data in readium-shared-js accepted format.