PDXjs January Meeting Recap
The inaugural meeting of the Portland JavaScript Admirers was a big success. We started off the evening with a round of introductions.
After that we listened to several talks on the fine language that is JavaScript. I pulled out my copy of JavaScript: The Good Parts by Douglas Crockford and went over some of the tips from the book on how to write great JavaScript code. I focused on how and why to avoid global variables - which can sneak up on your JavaScript code if you are not careful.
For example, you may know that variable declaration in JavaScript is optional. But did you know that variables that are not declared become global?
Another tricky case is the this keyword, which is used in method definitions to access attributes of the object that the method is attached to. But this is actually re-assigned every time the method is invoked. So if the method is invoked as a function instead of as a method, i.e.
var f = object.method; f();instead of
object.method();then this is assigned to the global object for the execution of f. So any attributes set on this then become global variables, and any attributes read from this are read from the global namespace instead of from object.
The code examples that I am pointing at in the video are online at http://gist.github.com/64478.
Scott Becker told us all about the features of SproutCore, which is an MVC framework for browser-side applications. Among other things, SproutCore allows you to set up models for your data, which can act as an intermediary to transfer data to and from a server, or that can store data locally using something like Google Gears. Changes made in the model data automatically update data in your views, and vice versa, through the use of Key-Value Coding. Instead of directly accessing attribute values, you use object.get(key) and object.set(key, value). This allows SproutCore to do all kinds of magical stuff for you.
Views in SproutCore are things like forms and form elements, buttons, file selectors, and content areas. Instead of using the browser’s form elements and buttons, SproutCore renders these as images to achieve a very slick-looking interface that is consistent across all browsers.
Using Key-Value Coding with views, you can do stuff like get input from your user via a form, and display a live preview of the content he enters that is updated in real time, with very little work on your part.
Unfortunately the batteries in our camera died partway through Scott’s talk. So there are a few minutes missing from the middle.
The slides from Scott’s talk are online at http://www.slideshare.net/joydivider/sproutcore-a-next-gen-javascript-framework.
I went over the new features in jQuery 1.3. Many speed improvements have been made in this release. For example, the selector engine is 49% faster. And HTML injection into the document is a blazing 6 times faster. The new, faster selector engine has been broken out into its own project called Sizzle.
This release also includes a complete rewrite of the event system. In addition to the bind method for binding event handlers, jQuery 1.3 supports the most excellent live method. Using live, your event handler will be bound to all elements on the page that match a given selector, and any elements that appear in the future that match the same selector.
jQuery events are now a self-contained system layered on top of native events. And the whole thing is compliant with W3C protocols for event handling.
I also gave an introduction to jQuery in general for those who are not familiar with it. And we had a lively group discussion on why people might prefer jQuery over alternative libraries, like Prototype.
Finally, J. Chris Anderson graciously jumped in to give us an introduction to CouchDB, a document-oriented database. CouchDB stores all of its data as JSON. There is no schema, and there are no tables. Queries are performed using the MapReduce pattern and can be written as stored JavaScript procedures.
Because it is schema-less, CouchDB is not a great choice when you need a lot of relational features, like joins. But in cases where you have been frustrated by SQL, CouchDB can be a great choice. It excels at serving up very large datasets with a high number of concurrent queries.
J. Chris is a CouchDB developer, and is one of the authors of CouchDB: Rough Cuts Version. We will hopefully be seeing another talk from him on using CouchDB to create pure-JavaScript applications.
At the end of the evening we retired to the Green Dragon for drinks. (Video suppressed.)
If you are having any trouble with audio syncing in the flash player, I suggest downloading the MP4s directly. Click on the title in any of the videos to go to its page on Vimeo. There you can find the file download link in the lower-right area.
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