Some embodiments provide a program. The program receives a first request to perform a first function in a plurality of functions configured for execution by a web browser operating on a client device. The first function is implemented by a second function on the mobile device using native code. The second function is configured to emulate the first function. In response to the first request, the program further performs the second function. The program also receives a second request to perform a third function in the plurality of functions. The third function is implemented by a fourth function on the mobile device using scripting code compliant with a defined scripting standard. The fourth function is configured to emulate the third function. In response to the second request, the program further performing the fourth function.