Philosophy
Express is excellent. But every Express codebase eventually diverges: routes defined differently across files, validation scattered or missing, error shapes inconsistent between endpoints, no shared vocabulary between services. Teams spend energy on glue code instead of product logic.
BananaJS is the one shape your team agrees on. It sits on top of Express — familiar runtime, same deployment model — and adds decorator routing, automatic validation, typed error handling, and a DI-ready module system. The result: every endpoint in every service looks the same, behaves the same, and can be tested the same way.
Four ideas drive the product
⚡ Conventions over configuration
A @Controller class, Validation schema, a createModule binding — that is the full mental model. You do not configure a router, register error middleware manually, or wire validators to handlers. The framework does it; you write business logic.
🧩 Heavy is optional
The core is lean — routing, validation, responses, errors, DI. Everything heavier (ORMs, observability, auth, caching, rate limiting, multi-tenancy, WebSocket) is a plugin or a decorator behind a peer dependency. You install what you need; nothing else is in your bundle.
🏛️ DDD when you want it
Start with a flat controller. When the model warrants it, introduce createModule feature slices with domain entities, repository ports, and infrastructure adapters — no forced ceremony. The @banana-universe/ddd package and bjs generate module scaffold exactly this layered structure; you adopt at your own pace.
🤖 AI as a first-class citizen
The bjs CLI ships AI-assisted workflows: generate a layered module from a description or schema, review and scaffold tests, explain code, and more. The LLM layer supports Ollama (default), llama.cpp, OpenAI, and Anthropic. See AI commands.
What BananaJS is not
- A full-stack framework. It does not include templating, SSR, a built-in database, or opinionated auth. It gives you the HTTP layer and lets you choose everything else.
- A NestJS replacement. BananaJS is intentionally smaller. If you need its full reflection-based DI, module graph, interceptors, and pipes, NestJS is the right tool. If you want NestJS-style DX on a fraction of the dependency surface, BananaJS is built for that.
Read the Quickstart to see these ideas in code in five minutes.