Evaluation of boolean values in JavaScript

If you have a background in a strongly-typed language such as Java, you’ll be used to using logical operators only with boolean values/expressions. However, in most dynamically-typed languages this doesn’t have to be the case, due to the nature of dynamic typing: The type of the variable is often determined based on the context in which it is used.

With JavaScript there are actually two concepts at play when using logical operators: What is actually returned from the result of a logical operation, and how variables are converted to boolean values when the context requires it.

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Using cURL in PHP to access HTTPS (SSL/TLS) protected sites

curl-https-padlock

From PHP, you can access the useful cURL Library (libcurl) to make requests to URLs using a variety of protocols such as HTTP, FTP, LDAP and even Gopher. (If you’ve spent time on the *nix command line, most environments also have the curl command available that uses the libcurl library)

In practice, however, the most commonly-used protocol tends to be HTTP, especially when using PHP for server-to-server communication. Typically this involves accessing another web server as part of a web service call, using some method such as XML-RPC or REST to query a resource. For example, Delicious offers a HTTP-based API to manipulate and read a user’s posts. However, when trying to access a HTTPS resource (such as the delicious API), there’s a little more configuration you have to do before you can get cURL working right in PHP.

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Google App Engine for Java: First thoughts

google-app-engine-java

When Google launched App Engine about one year ago, many were excited about their expected move into the cloud computing space, but at the same time, dismayed that it only supported Python, a language seemingly favoured at the Mountain View-headquartered company.

However, Google was adamant that they would begin supporting new languages and began taking requests on their issue tracker for what language to support next. So, it was no surprise that support for Java was announced last week as part of an “Early Look” at the feature.

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Aspect-Oriented Programming

I’ve started looking at Aspect-Oriented Programming (AOP) recently, because of its potential for improving code readability and maintainability. This is mainly provided by the “separations of concerns” goal that AOP aims to achieve. To get started, I decided to jump in using the jQuery AOP plugin. Why jQuery/JavaScript instead of something more mature like AspectJ? Well, for one thing, I have spent quite a bit of personal time developing with JavaScript and it seemed like a logical place to get a good footing before diving deeper with something like AspectJ.

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Using the Basic Constraints extension in X.509 v3 certificates for intermediate CAs

It’s not often that you’ll be creating your own X.509 certificates for a web server, since any certificates that you create (self-signed or signed by your own CA) will not be trusted by most browsers (IE, Firefox, etc.) since they were not signed by one of the many Certificate Authorities (CAs) that have been automatically trusted by the browser. If you do decide to use one of these certificates on your web server, you’ll have to navigate through a Byzantine series of screens to “confirm” that you trust the server’s certificate. (Though this is annoying, it may be ultimately beneficial in today’s era of phishing and other malicious behaviour.)

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JavaScript Event Delegation

JavaScript Event Delegation is a technique you may have heard of. It’s a different way of using event handlers that offers clear benefits and is becoming more popular amongst web developers. I’ll give a brief overview of event delegation in JavaScript, along with why you should consider it. Note that this tutorial will use the great jQuery library (v. 1.3.1) for most examples.

Delegation

Delegation is a fairly well-known design pattern. In short, it is a way for a method to produce its result simply by calling a method on another object, thus delegating responsibility to that object to provide the functionality needed by the method. For example, a Cashier object could store a delegate object called Calculator. Calling Cashier.addToTotal(value) would simply delegate to the contained object, calling Calculator.addToTotal(value).

How is delegation different than inheritance? With inheritance, the subclass inherits all of the functionality/behaviour of the parent class. You may not want or need this; in the preceding example, it would not make sense to have Cashier extend from Calculator simply because we wanted the addToTotal() behaviour/functionality. Delegation allows the behaviour advertised by a certain object/class to be provided by another.

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Properly setting Axis Ranges and Data Scaling using the Google Chart API

The Google Chart API is a great way to dynamically create chart and graph images for any non-static data you might want to display to your visitors, such as stats for a runner’s training log.

Although you can use your own server-side solution for generating charts, using PHP’s GD Image Processing Library or even a fancy chart library like pChart, this can increase the drain on your server’s resources. Client-side solutions that utilize the canvas element and jQuery or Flash can be very nice and easy to use, but may slow down the browser if there are a lot of charts.

Google Charts offers a nice trade-off; by using their service you offload the processing and bandwidth and get back a simple PNG image, but you must learn to use the API. Additionally, there’s also the risk that the service may throttle you, even if there’s no current usage limit.

Problems specifying Axis Ranges – Data points are not changed!

The API for Google Charts essentially consists of passing different query string parameters and their values and getting back a PNG-format image. As a result of this, passing in parameters is a bit quirky, and information in the API guide is a bit sketchy in this respect.

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Google changes iGoogle, making gadget development more profitable

On Thursday, Google rolled out an update to its personalized home page service, iGoogle. Among other UI updates, the major new features were increased flexibility in what “gadgets”, the personalized “chunks” that make up an iGoogle start page, can do. This, in turn, allows developers much more freedom with what they can provide to the user through an iGoogle gadget.

Previously, gadgets could only occupy a small box that took up only a third of the screen. While this was okay for reading headlines or perhaps glancing at stock prices, it limited the usefulness of gadgets and the information that could be provided. For more detail, users would often have to click a link in the gadget that would take them away from iGoogle. While this is perhaps the proper use of a “start page”, Google may now see things differently.

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Google Chrome: What it offers

Google Chrome

After much speculation yesterday, marked by a leaked web comic and finally an acknowledgment by Google, Google Chrome, the much anticipated web browser, is here.

I encourage you to download it and give it a try, as I did as soon as it came out. Here are some of my initial impressions.

Overview

Google released a fairly long web comic that delves into quite a bit of detail about Chrome – it’s not your typical comic! Touted as being built “from scratch”, Chrome uses the WebKit rendering engine, the same one that powers Safari and Konqueror.

The first thing you notice is how minimal the “Chrome” or UI of Chrome is. If you’re used to a half-dozen toolbars, buttons and widgets all over the place, Chrome will seem like a greenfield to you. By default, there is only a tab bar and then an address bar containing back, forward, a combined reload-stop button and the address bar. There are also buttons for bookmarking a site and for page and browser settings. The bookmarks bar is not displayed unless you specifically change that setting.

Keyboard shortcuts are also present so that you don’t have to click through context menus. If you’re used to the keyboard shortcuts of Firefox and IE7 you’ll be pleased to know that most of them transfer over without change: Ctrl-T opens a new Tab, Ctrl-W/Ctrl-F4 closes a tab, Alt-D focuses the address bar and Ctrl-J opens Downloaded Files.

The address bar also functions as a search bar, and this combination just makes sense. It’s something I’ve always been doing using Firefox Quick Searches

By default the home/start page is set to set to show an Opera-style “Speed Dial” page containing most recently-accessed pages/bookmarks. You can also configure Chrome to restore the previous tabs/websites on startup, which is my personal preference ever since I started using Firefox.

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Decoding Google Maps Encoded Polylines using PHP

I’ve talked about the Google Maps encoded polyline format before. While there’s some nice utilities for encoding polylines that take the work out of implementing it yourself, I couldn’t find many polyline decoders.

This made it somewhat tedious to decode them, as the only way to get the original list of points was to create a GPolyline and then pull out the points from that object. This is not ideal since the work must always be done on the client side with JavaScript and using Google Maps.

To solve this, I quickly ported the algorithm over to PHP from the JavaScript source. Please feel free to download/modify/use this script.

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