dojo’s dynamic inclusion of the logic required to render pages is great. The line dojo.require("widget"), ensures that the code required to run “widget” will be ready to run.

There is a hidden cost to this - the underlying logic and requests to get the code from the server.

On a complex page that has a lot of widgets (more than 50% of the dijit widgets offered), it is worth considering the following tags:

<script type="text/javascript" src="dojo/dijit/dijit.js"></script>
<script type="text/javascript" src="dojo/dijit/dijit-all.js"></script>

Although dijit-all is large, it is compressed, and it has all the widgets. A single request can replace 50 or more requests. Each request has an overhead of about 15ms, even if the javascript is cached in the browser. It is definitely worth running a test with Firebug to see if you can realize any performance gains with this strategy.

The ideal solution is a custom build, but you can’t always solve problems the “best” way. Sourcing dijit.js and dijit-all.js, using a loading .gif, and configuring caching carefully reduced page load time to 1/3 of the initial value, and provided a more graceful load process.