How to split jQuery plugin over multiple files

Question

I'm writing a small CMS as a jQuery AJAX plugin and though it's by no means excessively long (currently about 500 lines) I can see it would be nice to be able to split it into separate files, one for each "subclass":

(function($) {
    $.fn.myCMS = function() {
        this.classOne = function() {
        ...
        }
        this.classTwo = function() {
        ...
        }
    }
})(jQuery);

In the example above, I would like to put the code for classOne in one file, classTwo in another and the myCMS "baseclass" in a third. Is it possible to achieve this with with something like this (in each of the "subclass" files)?

$.extend(myCMS,classOne = function() {
...
})

Many thanks,

JS

Answer 1

You want to add to the "plugin" with a private scope / separation of concern. This can be important for maintenance and long-term extensibility of your plugin-based web application, regardless of whether everything will be built into one file or multiple files.

You can create a private scope and extend an existing jQuery.fn method by attaching methods directly or by adding to the jQuery.fn.foo method's prototype

(function ($) {

     // instance method attached to the constructor function
     $.fn.myCMS.classOne = function () {

     };

     // or "shared" method attached to prototype
     $.fn.myCMS.prototype.classOne = function() {

     };

})(jQuery);

You can use jQuery.extend(), which in this case is really a "shorthand" for adding a method to the constructor instance as the first method above. You have to encapsulate whatever you're adding into an object (typically this would be an anonymous object):

$.extend($.fn.myCMS,{ classOne: function () { } });

From a design perspective if you have "classes" that need to get at the same closured variables frequently they should probably be part of the same function scope/closure, or you should expose getters and setters for those closured variables (perhaps with the _foo convention that shows they are intended to be used only by your code).

(function ($) {

    var foo = "foo!";

    // combined getter/setter
    // could also check arguments.length
    $.fn.myCMS._foo = function (value) {
          if (typeof(value) != "undefined") {
               foo = value;
          } else {
               return foo;
          }
    };

)(jQuery);

If you want to be a hacker and you need to get at closured variables from a different scope, I believe you can do so by executing these new methods with their own scope using .call() or .apply() from the other scope. I can try to whip up some samples of how this works, but it will be a good idea if you do your own research into how scope resolution works in these kinds of scenarios.

I believe you can "borrow" the scope from the original "plugin" method by using a with ($.fn.myCMS) { } construction but I am not 100% positive about that because I haven't done it myself, only read about it.

Answer 2

It will help to also look at jQuery ui code. For example, the progressbar plugin requires three files ui.core, ui.widget and ui.progressbar. Download the jQuery UI source bundle and look at the progressbar example under demos directory. (I couldn't find the simplified version hosted anywhere, but the source bundle has simplified examples)