Node Dependency Injection

Standardize and centralize the way objects are constructed in your application.
Inspired by the battle-tested Symfony DI container, built for Node.js & TypeScript.

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Why Node Dependency Injection?

Managing dependencies manually leads to tightly coupled, hard-to-test code. Node Dependency Injection gives you a powerful, flexible IoC container that wires your application together — keeping your classes clean, your tests simple, and your architecture solid.

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✨ Features

🔄 Autowire — zero-config DI for TypeScript	📁 Config files — YAML, JSON or JS
🏭 Factory pattern — flexible service creation	🏷️ Service tagging — group & inject by tag
💤 Lazy services — instantiate only when needed	🎨 Decorators — wrap services transparently
⚡ Compiler passes — transform the container at build time	🔒 Private services — encapsulate internals
🌳 Parent / Abstract services — share config via inheritance	🧩 Non-shared services — new instance per call
🌿 Environment parameters — %env(VAR)% support	🗑️ Deprecation warnings — mark services as deprecated
📦 Express middleware — first-class web framework support	🖥️ CLI — inspect & validate your container
🔀 Conditional services — register services based on env or other services	🗝️ Keyed services — named strategy pattern with registerKeyed
🔗 Autowire + Keyed — inject keyed services via parameter binds

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📊 Feature Comparison (NDI vs InversifyJS vs tsyringe vs Awilix)

Feature	node-dependency-injection	InversifyJS	tsyringe	Awilix
Config files (YAML / JSON / JS)	✅ Native	⚠️ Programmatic-first	⚠️ Programmatic-first	⚠️ Programmatic-first
TypeScript autowire without decorators	✅ Native	❌	❌	❌
Keyed services (named strategy groups)	✅ Native	⚠️ Via custom patterns	⚠️ Via tokens/patterns	⚠️ Via aliases/patterns
Conditional service registration	✅ Native	⚠️ Manual logic	⚠️ Manual logic	⚠️ Manual logic
Compiler passes / compile-time transforms	✅ Native	❌	❌	❌
Service tags and tagged lookup	✅ Native	⚠️ Manual metadata patterns	⚠️ Manual token patterns	⚠️ Naming/registration patterns
Private services	✅ Native	⚠️ Container conventions	⚠️ Container conventions	⚠️ Container conventions
CLI container inspection / validation	✅ Native (ndi)	❌	❌	❌
Parent / abstract definitions	✅ Native	⚠️ Composition-based	⚠️ Composition-based	⚠️ Composition-based
Lazy services	✅ Native	✅	⚠️ Partial patterns	⚠️ Partial patterns

Legend: ✅ built-in, ⚠️ possible with custom conventions or extra setup, ❌ not available as a first-class feature.

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🚀 Installation

npm install --save node-dependency-injection

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🏁 Quick Start

Register services and wire them together in seconds:

import { ContainerBuilder } from 'node-dependency-injection'
import Mailer from './services/Mailer'
import ExampleService from './services/ExampleService'

const container = new ContainerBuilder()

container.register('service.example', ExampleService)
container.register('service.mailer', Mailer).addArgument('service.example')

await container.compile()

const mailer = container.get('service.mailer')

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🔄 Autowire (TypeScript)

Zero-configuration dependency injection — NDI reads your TypeScript type annotations and wires everything automatically:

import { ContainerBuilder, Autowire } from 'node-dependency-injection'

const container = new ContainerBuilder(false, '/path/to/src')
const autowire = new Autowire(container)
await autowire.process()
await container.compile()

// Retrieve by class — no string IDs needed
import SomeService from '@src/service/SomeService'
const service = container.get(SomeService)

// Or retrieve by ID with an explicit type
const typedService = container.get<SomeService>('service.some')

Production tip: dump the autowired config to a YAML file and load it directly in prod — no TypeScript scanning overhead.

if (process.env.NODE_ENV === 'development') {
  const autowire = new Autowire(container)
  autowire.serviceFile = new ServiceFile('/dist/services.yaml')
  await autowire.process()
} else {
  const loader = new YamlFileLoader(container)
  await loader.load('/dist/services.yaml')
}
await container.compile()

The generated services.yaml uses human-readable service IDs derived from the file path relative to your source root (e.g. Service/Mailer), making it easy to review, audit, and debug your application's service graph:

# services.yaml (human-readable — default since v4.0)
services:
  Service/Mailer:
    class: /Service/Mailer
    arguments:
      - '@Service/Transport'
  Service/Transport:
    class: /Service/Transport
    arguments: []

Service ID strategy

Strategy	Default	Service ID example	Description
readable	✅ v4.0+	Service/Mailer	Path relative to defaultDir, extension stripped
legacy	v3.x	U2VydmljZS9NYWlsZXI=	Base64-encoded absolute path

To opt back in to the legacy strategy (e.g. for gradual migration):

const autowire = new Autowire(container)
autowire.makeIdLegacy() // switch back to base64-encoded IDs

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🗝️ Keyed Services

Keyed services let you register multiple implementations of the same interface under a named group, then retrieve a specific one by key or inject the entire group as a Map.

Programmatic API

import { ContainerBuilder, KeyedReference, KeyedGroupReference } from 'node-dependency-injection'
import StripePayment from './payments/StripePayment'
import PaypalPayment from './payments/PaypalPayment'
import CheckoutService from './CheckoutService'
import PaymentRouter from './PaymentRouter'

const container = new ContainerBuilder()

// Register implementations under the 'payment' group
container.registerKeyed('payment', 'stripe', StripePayment).setDefault(true)
container.registerKeyed('payment', 'paypal', PaypalPayment)

// Inject a specific key
container.register('checkout', CheckoutService)
  .addArgument(new KeyedReference('payment', 'stripe'))

// Inject the full group as a Map<key, instance>
container.register('payment.router', PaymentRouter)
  .addArgument(new KeyedGroupReference('payment'))

// Retrieve by key or get the default
const stripe = container.getKeyed('payment', 'stripe')
const defaultPayment = container.getKeyed('payment')          // returns the .setDefault(true) one
const allPayments = container.getKeyedGroup('payment')        // Map { 'stripe' => …, 'paypal' => … }

YAML configuration

services:
  payment.stripe:
    class: 'payments/StripePayment'
    keyed:
      group: payment
      key: stripe
      default: true

  payment.paypal:
    class: 'payments/PaypalPayment'
    keyed:
      group: payment
      key: paypal

  checkout:
    class: 'CheckoutService'
    arguments: ['@keyed(payment, stripe)']

  payment.router:
    class: 'PaymentRouter'
    arguments: ['@keyed_group(payment)']

Autowire integration

When using Autowire you can inject keyed services into typed constructor parameters by registering a bind whose name matches the parameter name:

// TypeScript service
export default class CheckoutService {
  constructor(private readonly payment: IPaymentService) {}
}

export default class PaymentRouter {
  constructor(private readonly payments: Map<string, IPaymentService>) {}
}

container.registerKeyed('payment', 'stripe', StripePaymentService)
container.registerKeyed('payment', 'paypal', PaypalPaymentService)

// The bind name must match the constructor parameter name exactly
container.addBind('payment', new KeyedReference('payment', 'stripe'))
container.addBind('payments', new KeyedGroupReference('payment'))

const autowire = new Autowire(container)
await autowire.process()
await container.compile()

// container.get(CheckoutService).payment  → StripePaymentService
// container.get(PaymentRouter).payments   → Map { 'stripe' => …, 'paypal' => … }

Note: binds take priority over type-based resolution. The same mechanism works for scalar values — container.addBind('apiKey', '%env(API_KEY)%') — so keyed service binds fit naturally into the existing bind API.

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📁 Configuration Files

Prefer declarative config? Use YAML, JSON or JS:

# services.yaml
services:
  service.example:
    class: 'services/ExampleService'

  service.mailer:
    class: 'services/Mailer'
    arguments: ['@service.example']

import { ContainerBuilder, YamlFileLoader } from 'node-dependency-injection'

const container = new ContainerBuilder()
const loader = new YamlFileLoader(container)
await loader.load('/path/to/services.yaml')
await container.compile()

const mailer = container.get('service.mailer')

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🔀 Conditional Services

Register services only when specific conditions are met — evaluated at compile() time.

import { ContainerBuilder, Condition } from 'node-dependency-injection'

const container = new ContainerBuilder()

// Register only when an environment variable is set
container.register('cache.redis', RedisCache)
  .setCondition(Condition.envExists('REDIS_URL'))

// Fallback: register only when another service was NOT registered (TryAdd)
container.register('cache.memory', InMemoryCache)
  .whenMissing('cache.redis')

// Register only when a sibling service IS registered
container.register('metrics', Prometheus)
  .whenServiceExists('http.server')

// Combine conditions
container.register('feature.x', FeatureX)
  .setCondition(Condition.all(
    Condition.envEquals('NODE_ENV', 'production'),
    Condition.envExists('FEATURE_X_ENABLED')
  ))

await container.compile()

The same conditions are available declaratively in YAML:

services:
  cache.redis:
    class: 'services/cache/RedisCache'
    when:
      env_exists: REDIS_URL

  cache.memory:
    class: 'services/cache/InMemoryCache'
    when:
      missing: cache.redis

  metrics.prometheus:
    class: 'services/metrics/Prometheus'
    when:
      service_exists: http.server

  logger.verbose:
    class: 'services/logger/VerboseLogger'
    when:
      env_equals: { var: LOG_LEVEL, value: debug }

See the Conditional Services wiki page for the full API reference and advanced usage.

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📦 Ecosystem

Express Middleware

Use NDI seamlessly with Express — retrieve the container directly from any request:

npm install --save node-dependency-injection-express-middleware

import NDIMiddleware from 'node-dependency-injection-express-middleware'
import express from 'express'

const app = express()
app.use(new NDIMiddleware({ serviceFilePath: 'services.yaml' }).middleware())

Express Middleware Documentation

CLI

Inspect and validate your container from the command line:

# Validate a config file
ndi config:check /path/to/services.yaml

# Inspect a specific service
ndi container:service /path/to/services.yaml service.mailer

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📖 Documentation

The full documentation lives in the project wiki, including guides on:

• Getting Started
• Autowire
• Keyed Services
• Configuration Files
• Compiler Passes
• Conditional Services
• Tagging Services
• Factory
• Lazy Services
• Decorators
• And much more...

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🤝 Contributing

Contributions are welcome! Please read the contribution guide before submitting a pull request.

• Open an issue
• View milestones
• Changelog

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🙏 Credits

Inspired by the Symfony Dependency Injection component — a special thanks to the Symfony team for their outstanding work.

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MIT License  ·  Made with ❤️ by @zazoomauro