Get javascript file with jQuery. Also let that the file be cached.

jquery-get-js-script.js

jQuery.cachedScript = function(url, options) {
 
  // allow user to set any option except for dataType, cache, and url
  options = $.extend(options || {}, {
    dataType: "script",
    cache: true ,
    url: url
  });

  // Use $.ajax() since it is more flexible than $.getScript
  // Return the jqXHR object so we can chain callbacks
  return jQuery.ajax(options);
};