I’ve heard a rumor from a trusted source that the next version of Learning Ext JS is being written, and it may be titled Learning Ext JS 3.0. It will be updated to reflect working with version 3.x of the library, and have at least three new chapters added. If it is published in 2010, this could be a great year for Ext JS books, with Ext JS in Action scheduled to go to print in June.
Three Pillar Global sponsored their first Ext JS meetup earlier this week, and they were kind enough to invite me to give one of the presentations. Thanks to Patrick Sheridan (@sheridap) of Three Pillar for pulling it together, and providing the delicious pizza! My presentation was inserted between Shea Frederick and Jay Garcia’s. Pretty good company, I’d say.
Pat started off discussing “Design for Use“. Then Shea told us all about “Practical Ext JS Debugging“.
My talk is titled “Five Tips to Improve Your Ext JS Application”. I briefly touch on five distinct strategies to use to make your code more maintainable and reusable. Below the slides is a short discussion of each topic:
Explicitly define your own “classes” as you build your UI. This will allow your code to be more reusable, testable, and maintainable. It’s really easy to do, and along with namespacing your files and only defining one component per file, this approach will lead to amazingly clear directory structure.
Sometimes also known as an “event broker”, this is a simple object used to centralize all events. The example in the presentation is the “simplest event manager you can build with Ext JS”. I like to use at least one in every project to simplify the coding when someone inevitably asks, “can you make it do X every time the user does Y?”
Fire an event on the MyApp.eventManager
Anytime you need to “hack” the framework, do your work in a special file (or dir): call it “overrides”. Then when you test your upgrade to the next version of Ext JS, all the integration points to inspect are in one place. I also included my idea of a standard directory layout. I think it works well with the idea of “Namespace Segmentation” as discussed in Chapter 16 of Ext JS in Action.
Write good JavaScript code. Use JSLint. Read The Good Parts and Even Faster Websites.
This is a tricky one. If you have the choice, build your application in two tiers – Ext JS, and web service. They don’t even have to share the same endpoint! A cleaner design emerges when you separate the concept of the Ui and the data. If you work on a project that already muddles the two with server-side script tags and generation of Ext JS configs with “helpers”, then make it a goal to write all new code in the two-tier style. Put your Ext JS code in .js files. And only communicate with the server via JSONStores and Ajax requests.
The winner_picker UI.
Shea brought a few copies of Learning Ext JS, and Jay brought a few vouchers for an early access copy of Ext JS in Action. We needed a way to give them away – so, I dreamed up a simple app to randomly choose an attendee. To make it fun, I wanted to have a slick animation to randomly highlight attendees names for a few seconds before the choice is shown.
In less than an hour or so, here’s the Ext JS app I made: it’s a grid with an Array Store (attendees were entered manually), and one button that kicks off the process. And the silly animation: every 10ms, a grid row is selected at random and highlighted. The delay is slowly ramped down for effect. After a few seconds, the last random choice is made, and a message box is shown with the winner’s name. The code is on github, and I encourage you to fork the project and improve it, for no other reason than practice (basic knowledge of git is easy to get). The Five Tips can be applied to this tiny project just as well as they can to your large enterprise project!
I think it was a successful event, and I hope to be involved in the future. There were a handful of intense discussions afterwards – it’s good to be a part of a passionate community! If you are in the Baltimore area, come on out to our JavaScript meetup and hang out with us on the first Wednesday of every month. We meet at the Beehive in Canton. If you are in NOVA and want to help build the Ext JS meetup scene there, get in contact with Pat (@sheridap) or Jay (@tdgi).
I’d love to hear what you think about the Five Tips. Feel free to comment here, or on the slideshare page!
JSLint is one of the most valuable tools for a JavaScript developer. Short of being a “compiler”, it’s a “code quality tool” that can keep you from doing things that may come back to haunt you in the future. I’ll leave the detailed explanation to the author, Douglas Crockford – I assume you’re reading this because you want to integrate jslint into your Rails project and run it on the command-line!
To run jslint as a rake task in your Rails project, you’ll only need a few things:
So let’s get it set up. First, the java. Drop into a shell on your development system (or build system, wherever you want to run jslint), and make sure you have access to the java runtimes (run java -v, or which java). If not, go get it. Don’t be afraid, it’s easy.
Next you’ll need Rhino, the javascript execution environment. There are many js implementations (spidermonkey/treemonkey, v8, etc), but Rhino is the one that Crockford chose when he wrote the extension to jsunit that loads a file to be parsed. Its a jar file, go get it and put it into your project as vendor/rhino.jar.
Now you need Crockford’s jslint code. There are two parts: one is jslint.js, and the other is the Rhino extension (rhino.js). We will need both of these, and I’ve found it’s easiest when they are combined into one. Concatenate rhino.js to the bottom of jslint.js and save as vendor/jslint.js.
Hey, we’re almost there! Now you just have to add the rake task to your project.
Drop this gist into an existing Rakefile, or rake task. If you don’t have any rake tasks, then simply save this as lib/tasks/jslint.rake. Rake will find it in your project automatically. Run rake -T to confirm.
A short explanation: it finds all the js files you want to inspect, and runs jslint on them one at a time, printing out failures. Line 6 is the key line – you can change two parts of this to suit your project. First, the list of files to check is created using a Dir glob. My example gets all *.js files under /public recursively (**). Then the second part of that line is used to reject js files you DO NOT want to inspect. Frameworks, 3rd party code, for example (although it can be fun to run jslint on your framework code to see their level of quality). This example excludes the ExtJS installation.
Now youre ready to run
and enjoy the benefits of quality-checking your JavaScript code! And since you’ve just built a rake task that returns 0 or 1, it can be easily integrated into you automated or continuous build process. Heh heh – now the build will fail and everyone will know who doesn’t use triple-effing-equals! (see slide 13 of Naked JavaScript)
Enjoy command-line jslint. And if you develop using TextMate, I highly recommend integrating jslint into that as well.
(I’ve been thinking and talking about this for too long. Inspiration to finally get command-line jslint set up came from reading this stackoverflow earlier today.)
I am an independent consultant currently located in Baltimore, MD. I'm available for hire for Ruby on Rails and Ext JS web projects!
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