title,description,thumbnailUrl are class selectors
means speacify with dot(.)
like this
var title = $(cur).find(".title").text();
var thumbnailUrl = $(cur).find(".thumbnailUrl").text();
var description = $(cur).find(".description").text();
Suppose it is all are id selector
means put #
before on it
var title = $(cur).find("#title").text();
var thumbnailUrl = $(cur).find("#thumbnailUrl").text();
var description = $(cur).find("#description").text();