i developed a game using
iPhone 4s ,
android nexus) the FPS was dropped to 20 - 22 on
iPhone (max) how to optimize it to increase the FPS to 30 on mobile .
Generally slow downs are an inevitable part of using a mobile browser. There just isn't as much grunt on a phone, and mobile browsers are not yet as natively accelerated as their desktop counterparts. This is changing though (iOS 6 for example has made great leaps).
For now though, generally you need to profile and optimize your code. Try to use some isolated testing to understand what's causing the lag. Some general tips: