How will you seperate your code on basis of plateform ?

Before we get into the strategies you should adopt, let's look at the mechanics of handling cross-platform coding within Titanium. This includes:

• Platform identification
• Recognizing platform-specific APIs and properties
• Handling platform-specific resources

Platform identification

Titanium provides platform-identification properties in the Ti.Platform namespace that you can use for conditional branching within your code. These are:

Property	Description	Sample values
Ti.Platform.name	Returns the name of the platform returned by the device	iPhone OS for iPhone or iPod, android for Android, returns thenavigator.userAgent string on Mobile Web
Ti.Platform.osname	Returns an abbreviated identifier of the platform	iphone for iPhone or iPod, ipad for iPad, android for Android, andmobileweb on Mobile Web
Ti.Platform.model	Returns device model identifier	iPhone 3GS or iPod Touch 2G or Droid (unsupported on Mobile Web)

http://docs.appcelerator.com/titanium/3.0/#!/guide/Supporting_Multiple_Platforms_in_a_Single_Codebase