Simple lazy evaluation pattern

jquery.cache.js

(function($){
  $.fn.cache = function (key, create, use){
      var data = this.data(key);
      if (!data){
         data = create();
         this.data(key, data);
      }
      return use(data);
    };
})(jQuery);

usage.js

/*
 *  Sample based on:
 *  bocoup-training-more-efficient-event-handlers.js https://gist.github.com/cowboy/4773621
 *
 */
$("form").on("click", "button", function(event) {
  event.preventDefault();
  var button = $(this);
  button.cache(
    "countdown",
    function(){
      data = {};
      data.numberElem = button.find(".number");
      data.number = Number(data.numberElem.text());
      button.data("countdown", data);
      return data;
    },
    function(data){
      data.number = data.number - 1;
      data.numberElem.text(data.number);
      if (data.number === 0) {
        button.prop("disabled", true);
        button.removeData("countdown");
      }
    }
  );
});