Stubblog

Very often, different controllers require different javascript, and while you could just put all your javascript in your application.js file, this doesn’t doesn’t lend itself to anything more than the most basic of applications. It becomes very large, and hard to maintain.

The solution I use is to include any global javascript (prototype etc) in my application.rhtml and then use the controller name to load any specific javascript

<%= javascript_include_tag ‘prototype’ %>
<%= javascript_include_tag “application” %>
<%= javascript_include_tag controller.controller_name %>

The problem starts when you throw something like Yahoo’s YUI framework into the mix, with it’s many components and javascripts you can easily add some serious overhead if you include every one in the global application, the ones you don’t need just bloat your application and slow down page loads.

In the past, in other languages I’ve always solved the problem by passing the required libraries into the XSLT and letting it transform that into script tags, You could construct and array and use that in the view to load the various bits of javascript.

The engineers at Yahoo! have obviously run into the same problem, and recently introduced the YUILoader component, which lets you load any javascript the page may require, and if that happens to be YUI components, it’ll also load any dependencies they require too. This is also a great way of integrating YUI with rails, without bloating your app, and without creating convoluted bespoke solutions.

To start with, you need to include the YUILoader itself in your applications view, but before we go any further, I’ll just point out that while you can use the Yahoo! hosted versions and probably should, for development I prefer to have a local copy to use just in case net access isn’t available. I put a copy (actually, I symlink it.) in public/javascript/yui, my application.rhtml has something like this in it:

<%= javascript_include_tag ‘prototype’ %>
<%= javascript_include_tag “application” %>
<%= javascript_include_tag ‘yui/yahoo-dom-event/yahoo-dom-event’ %>
<%= javascript_include_tag ‘yui/yuiloader/yuiloader-beta’ %>
<%= javascript_include_tag controller.controller_name %>

You don’t need to include yahoo-dom-event, but if you don’t YUILoader will try and grab it from the internet, regardless of where you tell it ‘base’ is.

In your ‘controller_name.js’ you need to initialise the loader, tell it what to load and finally tell it what to do once it’s loaded them.

var init = function()
{
var loader = new YAHOO.util.YUILoader({
require: ['container', 'element', 'button', 'calendar'],
onSuccess: function() {
// Put your code here to initialise any
}
});

loader.insert();
};

// Use whatever method you like to make sure the page has finished loading.
YAHOO.util.Event.addListener(window, ‘load’, init);

This way you can seperate your javascript into seperate files to match your controllers, and keep your app lean by only loading the javascript you need, when you need it.