PG2

38 Chapter 2 PhoneGap Development, Testing, and Debugging
be working on Android, but not BlackBerry, so I used the alert to help confirm my
suspicion and to help test different approaches as I attempted to fix the problem.
The problem with this approach is that when you fill your buggy code with alerts,
you’re constantly interrupting the application flow to dismiss the alerts as they
come up. For a simple problem, this approach works pretty well, but when debugging
more troublesome errors, you will need an approach that allows you to let the
application run and then analyze what is happening in real time or after the application
or a process within the application has completed, without interrupting the
application. PhoneGap applications can do this through the JavaScript console
object implemented by the WebKit browser rendering engine.
Using the console object, developers can write messages to the browser’s console,
which can be viewed outside of the running program through capabilities
provided by the native SDKs or device simulators or emulators. The console
object has scope at the window level, so it’s essentially a global object accessible
by any JavaScript code within the application. WebKit supports several options;
the most common ones used are as follows:
• console.log("message");
• console.warn("message");
• console.error("message");
Example 2-1 shows a sample application that illustrates the use of this feature.
Example 2-1
function onBodyLoad() {
document.addEventListener("deviceready", onDeviceReady,
false);
}