Tag Archives: JavaScript

HTML5 Canvas Layering

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I have recently begun to study a couple different ideas to ease the pain of more complex animations using the HTML5 canvas element. Primarily, I have been focusing on layering – stacking individual transparent canvas elements – to achieve a robust effect and help manage individual objects without having to redraw the entire pane with every refresh. In the orbit example above, the center sphere and background are drawn statically on the bottommost layer, while the animation of the satellites is calculated and drawn on a second layer. By clicking on the demo, you can toggle the visibility of the animation layer. If you cannot see the animation at all, you may want to consider picking up a real web browser: Firefox or Chrome are always good options.
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Introducing JSWidgets

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I have been, for some time, working on a concept that would allow the average JavaScript user to create robust, interactive applications with ease. A daunting task, I know, but having tried to implement so many bloated libraries for simplistic interaction, I wanted to create a way for the beginning or average web developer to create advanced modules quickly. One of the biggest things I have noticed in recent years is the lack of attention given by many to the client side code structure. With this project, I hope to help educate developers a bit more in the necessity of code separation, documentation and reuse of code.

I have been asked if I’m guilty of reinventing the wheel, and it is possible that you may think so, but I feel this offers a level of uniqueness not found in a library this lightweight. In fact, the purpose of this library is not to be a solution to the need in and of itself, but rather it is intended to lay the groundwork for developers to quickly extend their own widgets and have them working in no time. While I am introducing this library in its infancy, I am already in the process of overhauling the template structure to leverage Underscore.js, the most lightweight and robust JavaScript template engine I’ve found to date.
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Smart Resize Script for Adobe Photoshop CS4

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If you have ever had a massive number of images you needed quickly and accurately resized for export, upload to web or any other reason, you may well be familiar with the concept of recording Photoshop Actions. These beautiful little tools allow you to literally record a macro (series of user actions) that can then be applied to the currently active document. Further, when combined with the “bulk” feature of Photoshop, you can apply this action to an entire directory and apply the action to each and every image, exporting the resulting image to a specified location as well. Overall, this is an extremely useful tool and can save minutes — if not hours — of work, but it has one tiny limitation that has been a bane to me for some time. When recording an action, you must specify either a height or a width on resize: there is no way to conditionally apply your length to the height OR width dependent upon ratio. Enter the Photoshop Script.
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How to Manually Trigger Events in JavaScript

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Occasionally, I find need to be able to manually trigger a predefined JavaScript event from within the context of a web application. Those of you who didn’t understand that first statement may want to stop reading now or risk suffering from extreme boredom, but those who actually have encountered the same challenge in coding, please read on!

Let’s examine a possible scenario that could merit actually taking hold of the reigns on individual event calls. Consider the situation that you have devised a very user friendly data entry form, and in conjunction with specifications, you have a select box that triggers certain fields to be visible based on user selection. Typically, you would have simply attached a listener to the select box’s onchange event that checks the value of the field and performs the necessary showing and hiding. So far, we have done nothing difficult or out of the ordinary.

Now, suppose you also have need to be able to populate the form with a preexisting data set and get your form to behave in the same way. You could always write an onload listener for the body of your page that runs all the field checks and manipulates the fields accordingly, and in most cases, this may not be a poor solution. However, when loading dynamically via AJAX or other method, the onload event may not be triggered, and therefore, neither is your form updated.
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jQuery Slideshow Plugin Update

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I have finally found a few spare minutes to refactor the Google Code Project I started for my jQuery plugin last year. While I still am far from where I want to be with it, I have managed to set the plugin into a fully OOP codebase and add in events and the capability for custom handlers on those events. My hope is that people will now be able to find a bit more usability to the slideshow, since it is fully customizable. Feel free to swing by my Google Code page and let me know thoughts or ideas on ways to improve the slideshow as it evolves.

JavaScript Library Nightly Builds, SymLinks and Auto-Updates

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Something has been bothering me for some time, and I finally took the time to resolve the issue once and for all – relatively speaking. As mentioned in my previous post, I have had opportunity to work with multiple different JavaScript libraries, and I often find myself running behind on the newest bug fixes for a given module. Many of the library development teams offer a nightly build available to checkout via SVN or Git (usually by way of GitHub), and I devised a way to automatically update my shared repositories among all the domains on my server. While not rocket science, nor an entirely new idea to most of you, it is quite helpful to me, and I thought I’d share my method here.

There are actually four steps involved with this update, so I apologize in advance if this gets too long.

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JavaScript libraries: jQuery vs. ExtJS

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Often I have been asked which JavaScript library I prefer over all other, and the answer is not as easily orated as one might expect. Occasionally, I actually find someone willing to spend the time and thought involved with seeing the answer through to its conclusion. To avoid any undue future banter, I thought I would put my thoughts concerning the matter down in writing and simply reference this post when the topic is breached.

No, this will not be a comprehensive discussion and review of all available JavaScript libraries, but hopefully it will be sufficient to drive people to view the topic with a bit more of an open mind. Also, I must alert those who have come looking for a definitive answer from me: you will not receive a single library of choice here, but rather you will be given some insight to different perspectives requiring careful consideration when each library is being reviewed.
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jQuery Plugin: gwSlideshow launched

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A while ago, I wrote a jQuery based slideshow that I shared with some friends, and I ended up getting a pretty good response to it – enough to merit making a full plugin with it. Here is the initial launch of the plugin and project, and I’d love to get any feedback pertaining to usability and additional features.

The intent is to remain very lightweight but flexible, and so far, that seems to be met. Following, you will find links to my Google Code project page as well as a sample script that demos the working slideshow. For any additional questions, please feel free to contact me.

Google Code: http://code.google.com/p/gw-slideshow/
Demo: http://code.guahanweb.com/jquery/demos/gwSlideshow.html

Enjoy!

Optional Config Objects in JavaScript OOP

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Well, one of the challenges in writing our custom JavaScript library for this next release of our CMS at work has been to come up with a modularized approach to our objects that can be followed precisely while still allowing a measure of flexibility to the end developer (Imagine that! Actually trying to support some framework style design principles in JavaScript!). Anyway, what has been one of the most challenging pieces to the puzzle has been to appropriately handle configuration objects passed to constructors that override specific, default behavior of the object.

No, the challenge was not so much handling a config object proper — that is relatively easy. Where the challenge began to really take shape was in allowing a user to provide specific pieces of optional data and only use the valid pieces of the config object to override existing default values while ignoring the rest so as not to cause any JavaScript errors to be thrown elsewhere in the script. For a quick example, let’s say we have the following data object that loads itself up using an Ajax call (NOTE: all examples in this post are using the ExtJS lib).
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Writing a Reusable AJAX Handler

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Due to the number of questions I receive on various forums as well as the number of times I have run into the need for an AJAX response handler in my own work, I decided I would share one of my solutions in the hopes that it will save someone else some time as well. I assume, if you are reading this, that you have a basic knowledge of AJAX and the principles guiding the technology. In addition, basic understanding of how libraries such as jQuery perform AJAX queries and callback functions in JavaScript is a plus. For further reading on these prerequisites, check out this Google search and the jQuery docs.

After manually handling my responses in multiple projects, I finally decided to write a JavaScript object that could handle the XML responses for me and return me a usable object to my callback function. Enter the AJAX Handler object. I decided to let jQuery handle the actual requests for me, but I wanted a way to easily parse out my response, checking for errors and handle them accordingly. The result was something I have been able to use numerous times in different projects. To simplify things, let’s look at the code a piece at a time. At the bottom of this post, you will find the entire code. Continue reading →