Jsnes

jsnes is a JavaScript-based NES emulator that runs classic NES games in the browser or in Node.js. It provides cycle-accurate CPU emulation, frame-buffer-based video rendering, and sample-buffer audio synthesis, along with a ROM cartridge mapper abstraction for broad game compatibility.

The emulator exposes a programmable core with a simple API for controlling emulation state, capturing screenshots, and managing save data. It supports keyboard control remapping at runtime, with settings persisted to localStorage, and offers state serialization for save and restore operations. Battery-backed SRAM changes are handled through a callback-driven persistence mechanism.

The project covers browser-based NES emulation with automatic canvas rendering and input handling, as well as headless emulation in Node.js for custom rendering pipelines. It also provides programmatic control over emulator state, including pause, resume, reset, and ROM reloading.

Features

Retro Game Emulation - Boots and runs classic NES games inside a web page with canvas rendering, audio, and input handling.

JavaScript Emulator Cores - Provides a JavaScript-based NES emulator with cycle-accurate CPU, PPU, and audio emulation for browser and Node.js.

Emulator Mapper Abstractions - Implements a pluggable mapper interface for broad NES cartridge compatibility.

Emulator SRAM Callbacks - Provides a callback mechanism for persisting battery-backed SRAM changes to external storage.

Save State Managers - Serializes complete emulator state into JSON for save and restore operations.

Emulation State Scripting - Provides a scripting interface for pausing, resuming, resetting, and reloading emulator state.

Web-Based Emulators - Runs classic NES games inside a web page with automatic canvas rendering, audio, and input handling.

Sample-Based Buffer Callbacks - Produces raw PCM audio samples from APU state through a sample-buffer-based pipeline.

Game Controller Remappers - Ships runtime keyboard remapping for NES controller buttons with localStorage persistence.

Emulation Session Control - Provides a simple interface for pausing, resuming, resetting, and reloading emulator state.

Programmable Emulator APIs - Exposes a simple API for controlling emulation state, capturing screenshots, and managing save data.

Cycle-Accurate Emulators - Implements cycle-accurate emulation of the 6502 CPU for precise NES hardware timing.

Emulator Frame Buffers - Generates complete 256x240 pixel frame buffers from PPU state for canvas drawing or external processing.

Keyboard Input Mapping - Translates browser keyboard events into NES controller button states via a configurable mapping table.

Node.js Emulation Cores - Runs NES CPU and PPU cycles programmatically in Node.js for custom rendering pipelines.

Game Keyboard Controls - Rebinds NES controller buttons to different keyboard keys at runtime with localStorage persistence.

Battery-Backed SRAM Persistence - Writes battery-backed SRAM changes to a callback for external save data storage.

Node.js Emulation Cores - Runs NES CPU and PPU cycles programmatically in Node.js for custom rendering pipelines.

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Features

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