Pass that Interview 1: Mimic a Class in Javascript

Javascript, unlike most object-oriented programming languages, does not have the concept of Classes. Instead, Javascript uses a model in which objects are created, cloned, and enhanced by creating copies of the objects (it’s loosely based on the Prototype pattern). There is a lot of power in this Prototypal system and people like Douglas Crockford have shown how Prototypal inheritance can be implemented in Javascript. This type of work is really cool; unfortunately it’s not generally well-known or well-understood and many developers wish to use Javascript to simulate the more familiar Classes & objects as seen in languages like Ruby and Java.

Due to this simulation being common practice, the following has become a fairly common interview question:

How do you create a class in Javascript?

The answer is a bit wonky; but pretty simple to follow:

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My Impressions of Google Web Toolkit (GWT)

Recently I’ve been asked several times for my opinion on the Google Web Toolkit (GWT)  and I’ve given much the same response each time. Now, it’s easier to consolidate my thoughts and share them with everyone via my blog.  I want to preface this post by stating, as I always do, that I have not taken a “deep-dive” look at GWT and, due to my stance below, I haven’t seen a reason to do such research.  I also want to state up-front that I don’t believe there’s any inherent flaw in GWT that prevents me from using it; nor do I think it’s “bad technology.” Finally, I’ve done my best to not allow my general distaste for Java influence my opinion of GWT.

I do not believe that GWT offers a unique value proposition as a platform that establishes any advantage over other Web development platforms such as traditional HTML and CSS or Adobe Flex. Additionally, there are some clear areas in which GWT lags behind these counterparts. Continue reading

How Self-Executing Anonymous Functions Work

In my recent post on creating a jQueryUI widget, I referenced the concept of self-executing anonymous functions. I’ve actually had a few questions come up at the office lately about how they work, so I figured turning it into a blog post might not be a bad idea. It’s an important concept in Javascript many don’t know about. Others know how to use them, but don’t really understand how or why they work. Today I’ll cover step-by-step how to go from a traditional function to a self-executing anonymous function; hopefully it will be clear at the end how these things work.
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Create a Basic jQueryUI Carousel Widget

One of the topics that was of great interest at #jqcon was jQueryUI and it’s impressive widget library.  What didn’t receive as much attention was how exactly to go about creating widgets that are compatible with jQueryUI.  In this first of a series of articles in jQueryUI development, we’ll cover the basics of creating a simple jQueryUI widget.  In future articles, we’ll look at how to pair widgets together using the Publisher / Subscriber (pub/sub) pattern.

This carousel is probably not quite robust enough to be deployed to production and I urge you to avoid copying and pasting this code into your live site. This basic carousel aims to teach you how to build one yourself as well as how to build a jQueryUI widget.

Create the Basic HTML Markup

To begin, we need a basic page and some photos thumbnails to work with. The thumbnails, as you’ll see later, can be any size you choose and our carousel will expand to fit them. Note especially that we’re only including some basic shell markup.  There are a few good reasons for this decision: First, it keeps our basic document clean and free of extraneous markup. Second, it is far less work for people implementing our widget—and fewer potential points of error in their process.

<div id="slide">
    <div>
         <img src="img/carousel/0_10.jpg" width="78" height="29" alt="" />
    </div>
    <div>
         <img src="img/carousel/0_11.jpg" width="78" height="58" alt="" />
    </div>
    <div>
         <img src="img/carousel/1_6.jpg" width="78" height="58" alt="" />
    </div>
    <div>
         <img src="img/carousel/1_4.jpg" width="78" height="58" alt="" />
    </div>
    <div>
         <img src="img/carousel/0_9.jpg" width="78" height="58" alt="" />
    </div>
</div>

For demonstration purposes, I’ve chosen the Cupertino theme available for download from the jQueryUI ThemeRoller application. You can choose any theme you desire—or create your own. Also, you can see I’ve created a reference to a  carousel.js file. We’ll create this file as we continue.

Create the basic framework of a jQueryUI plugin

Now that we have our basic structure in place for the carousel, we can begin to create the javascript that will control the animation and interaction. jQueryUI provides a great construct called $.widget() that will encapsulate all of the functionality of the widget within a single namespace and construct. Let’s start by creating a basic widget:

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Quick Javascript Tip: Pass an Options Hash

A quick Javascript tip that I pass along in a lot of code reviews is to make use of an options object as a hash to pass a large number of parameters to a function without writing each one individually.  For example:

function doSomething(id, someParameter, anArgument, optionC){ };

vs.

function doSomething(id, options){ };

By encapsulating the 3 additional parameters into an options object and passing them individually, you make for cleaner code.

A quick caveat is to check the options object to ensure that all of the necessary properties exist before running your function.