jQuery initData

jquery.ba-initdata.js

/*!
 * jQuery initData - v0.1pre - 5/18/2011
 * http://benalman.com/
 * 
 * Copyright (c) 2011 "Cowboy" Ben Alman
 * Dual licensed under the MIT and GPL licenses.
 * http://benalman.com/about/license/
 */

(function($){

  $.fn.initData = function(key, fn) {
    // Get the first element.
    var elem = $(this).eq(0);
    // Get the element data, if it exists.
    var obj = elem.data(key);
    // If it doesn't exist...
    if ( !obj ) {
      // Initialize the data from the function's return value.
      obj = fn.call(elem[0], key);
      // And set the data on the element.
      elem.data(key, obj);
    }
    // Return the data object.
    return obj;
  };

})(jQuery);

usage.js

// Do this:
var data = $('body').initData('key', function() {
  return {x: 1, y: 2};
});

// Instead of this:
var elem = $('body');
var data = elem.data('key');
if ( !data ) {
  data = {x: 1, y: 2};
  elem.data('key', data);
}

// Or this:
var elem = $('body');
var data;
elem.data('key', data = elem.data('key') ||  {x: 1, y: 2});