# Egg.js — Convention-Over-Configuration Node.js Framework for Enterprise

> A Node.js framework built on Koa by Alibaba, designed for large-team enterprise applications. Provides a plugin system, loader mechanism, and strict directory conventions that enforce consistency across codebases at scale.

## Install

Save as a script file and run:

# Egg.js — Convention-Over-Configuration Node.js Framework for Enterprise

## Quick Use
```bash
npm init egg --type=simple my-app
cd my-app && npm install && npm run dev
```

## Introduction
Egg.js is a Node.js framework developed by Alibaba's frontend infrastructure team. Built on top of Koa, it adds a convention-over-configuration layer with a robust plugin system that allows large engineering teams to share common patterns while maintaining flexibility for individual application needs.

## What Egg.js Does
- Enforces a directory-based convention for controllers, services, middleware, and config
- Provides a multi-process model with automatic worker management via egg-cluster
- Ships with a plugin mechanism that allows composing reusable business logic modules
- Supports environment-specific configuration with automatic merging
- Includes a built-in security plugin for CSRF, XSS, and SSRF protection

## Architecture Overview
Egg.js extends Koa with a loader system that scans conventional directories and wires up components automatically. The framework runs in a multi-process architecture: an agent process handles scheduled tasks and long-running connections, while multiple worker processes handle HTTP requests. The plugin system uses a dependency-declaration model where each plugin declares its dependencies and configuration schema. An application is itself treated as a plugin, and frameworks like egg can be further extended into company-specific base frameworks.

## Self-Hosting & Configuration
- Configure environment-specific settings in `config/config.{env}.js`
- Enable or disable plugins in `config/plugin.js` with simple key-value declarations
- Use `app/schedule/` to define timed tasks that run on the agent process
- Set `config.cluster.listen.port` to control the HTTP port
- Deploy with `egg-scripts start --daemon` for production process management

## Key Features
- Automatic multi-process management with graceful reload and zero-downtime restarts
- Loader mechanism that eliminates manual require statements and supports file-based routing
- Framework extensibility that lets teams build a shared base framework on top of Egg
- Built-in logger with automatic log rotation and structured output
- First-class TypeScript support with egg-ts-helper for declaration generation

## Comparison with Similar Tools
- **NestJS** — decorator-driven architecture inspired by Angular; Egg uses directory conventions and a loader system
- **Express** — minimal and unopinionated; Egg provides structure and enterprise patterns out of the box
- **Fastify** — performance-focused with a plugin system; Egg emphasizes team-scale conventions and multi-process orchestration
- **Koa** — Egg's foundation; Koa provides the middleware kernel while Egg adds the application layer

## FAQ
**Q: Is Egg.js still actively maintained?**
A: Yes, the core team at Alibaba continues to maintain it, with Egg 3.x bringing ES module and modern Node.js support.

**Q: Can I use Egg.js with TypeScript?**
A: Yes, use `npm init egg --type=ts` to scaffold a TypeScript project with full type inference.

**Q: How does the plugin system differ from npm packages?**
A: Egg plugins follow a specific contract (app extension, config schema, dependencies) that the loader wires up automatically, unlike generic npm packages.

**Q: Is Egg.js suitable for microservices?**
A: Yes, many teams use Egg with gRPC or HTTP-based service communication. The framework itself is process-model agnostic.

## Sources
- https://github.com/eggjs/egg
- https://www.eggjs.org/en

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Author: Script Depot