Battery Save / Save State

[Recognition101]

Awesome project!

I was going to extend it to allow controller input and state management. I've already figured out the controller stuff (I basically just create a ControllerInput object and write emulator.input = new ControllerInput()), but I don't know enough about NES architecture to know how to deal with state.

If I wanted the ability to save and load states or export and import a battery save, how would I go about doing that? What functions / files should I look into?

[koenkivits]

Thanks, and awesome to see you working with it! The things you're looking for have been on my "I wanted to do this, but I never really got around to it" list. :)

Battery save shouldn't be too complex to implement. Every Cartridge instance has ramData field, which is a Uint8Array. I guess you can read and store this data (from nesnes.cartridge, where nesnes is a NesNes instance) while it's running. If you want to load it again it should be a case of setting the ramData of the cartridge right after booting (but before running).
Does this help you? Please let me know if I don't make any sense. :)

Regarding save and load state: this is a little bit more complicated. I think it would require serializing the state of all the main components, and the code is not built for this. Right now the system state is a little bit all over the place. One solution would be to add serializeState and deserializeState method to all components involved, but I'm not sure how much work this would be. I also don't know how other emulators handle this.
By the way, if you want to know what the main components exactly are, look at initCore() in https://github.com/koenkivits/nesnes/blob/master/index.js . This is the method that basically initializes the entire system and all of its components.