debug javascript in android emulator with phonegap

Update Nov 2016: looks like this doesn't work anymore.

The easiest and one of the most powerful ways is using http://debug.phonegap.com (it uses Weinre in the background, if you care). You just

1. pick a random string, say r4nd0m,
2. inject <script src="http://debug.phonegap.com/target/target-script-min.js#r4nd0m"></script> into your index.html
3. visit http://debug.phonegap.com/client/#r4nd0m and you will instantly be debugging your mobile web app.

Things you can do (similar to Firebug or Web Inspector):

1. Viewing and changing the DOM
2. Editing CSS
3. Console for live debugging and running Javascript remotely.
4. Other stuff, like: storage, resources, timeline, profile, etc.

You could at least log debug stuff to the adb console by calling console.log() in JavaScript. Maybe that would suffice?

To view log output using adb, navigate to your SDK platform-tools/ directory and execute:

adb logcat

See logcat Command-line Tool

You can now use Chrome dev tools to remotely debug Android Phonegap apps! I wrote up instructions here: Remote debugging Phonegap apps with Chrome Dev Tools

Steps for Android emulator:

1. Navigate to chrome://inspect/ in Google Chrome on your desktop computer.
2. Locate Android emulator on Devices tab and click 'inspect' link

See also Get Started with Remote Debugging Android Devices