JSNES vs Nintendulator

JSNES is a free JavaScript library for emulating NES games in browsers and Node.js. Its Browser helper handles canvas rendering, audio, keyboard and gamepad input, and frame timing; the lower-level NES class allows custom rendering and audio handling in Node.js. ROM data can be loaded from a URL or from a string, Uint8Array, or ArrayBuffer. The API runs frames, accepts controller input for either player, resets, adjusts frame rate, and includes methods for moving and triggering the Zapper. Applications can serialize and restore emulator state with `toJSON()` and `fromJSON()`. The `onBatteryRamWrite` callback lets an application capture battery-backed SRAM writes for persistent game saves. Sound emulation is enabled by default, with a default sample rate of 48000 Hz, and an audio callback is available. The README provides npm installation for Node.js or Webpack and an unpkg script for browser use, as well as a React embedding example. JSNES is licensed under Apache-2.0; its GitHub Issues tracker accepts bug reports and feature requests.

Nintendulator is a free, open-source Win32 NES emulator written in C++. It aims to reproduce NES hardware behavior, including quirks and special cases. Supported formats include .NES, UNIF, FDS images in fwNES format, and NSF; mapper support uses external DLLs, with extra sound channels available for most games that provide them. Features include FDS image writing, Game Genie codes, customizable controllers including four-player setups, input movie recording and playback, AVI capture, and a debugger with simple breakpoint support. Savestates and battery-backed RAM are stored in the current user's Application Data folder, so the emulator can run without administrator privileges. The official release listed is version 0.980, dated January 1, 2019. Version 0.985 Beta is an unstable development build that may have significant bugs. Versions 0.985 and later have 32-bit and 64-bit editions and are officially supported on Windows 10 and later; older Windows versions may work, and recent builds are tested with Wine. Full-speed emulation is estimated to require a 1500MHz or faster CPU.