loose-di

Lightweight dependency injection container for JavaScript/Node.js.

Features (v5)

• Class, factory, and value providers
• InjectionToken — descriptive typed tokens
• @Optional — optional dependencies (returns undefined if unregistered)
• multi: true / container.getAll() — multiple providers for one token
• Plugin-based container extensions (resolve middleware, hooks)
• Lifecycle hooks: onInit (after deps injected) and onDestroy (on container shutdown)
• Property injection (@Inject on properties, $injectProps static, or props in provider config)
• Scopes: singleton (default), request, transient
• Module system with imports
• Async providers (factory can return Promise)
• Cyclic dependency detection
• @Injectable / @Inject decorators
• $inject / $injectProps static properties (no decorators needed)
• Request-scoped container fork + container.getOptional() / container.getAll()

Usage

const { Container, InjectionToken, defineModule } = require('loose-di');

const DB = new InjectionToken('Database');

const container = new Container();

container.provide({ token: DB, useFactory: async () => await createConnection() });
container.provide({ token: 'Config', useValue: { port: 3000 } });

// Optional dependency
class Logger {
  constructor(@Inject(DB) @Optional() db) {
    this.db = db; // undefined if DB not provided
  }
}

// Multi-provider (multiple values for same token)
container.provide({ token: 'Plugin', useValue: pluginA, multi: true });
container.provide({ token: 'Plugin', useValue: pluginB, multi: true });
const plugins = await container.getAll('Plugin'); // [pluginA, pluginB]

const db = await container.get(DB);
const maybe = await container.getOptional('Missing'); // undefined

Roadmap

| Version | Feature | |---------|---------| | v1 | Basic DI (class/factory/value, scopes, modules, cyclic detection) | | v2 | Property injection | | v3 | Lifecycle hooks (onInit, onDestroy) | | v4 | Plugin-based container extensions | | v5 | InjectionToken, @Optional, multi-provider |