First-DI

Lightweight and powerful dependency injection container for TypeScript applications

Overview

first-di is a modern, type-safe dependency injection container designed specifically for TypeScript applications. It provides a clean and intuitive API for managing dependencies with minimal configuration and zero runtime dependencies.

Key Features

• 🚀 Zero Dependencies - No external runtime dependencies required
• 💡 Two Operation Modes - Optional DI for simplicity, Classic DI for advanced scenarios
• 🔄 Multiple Lifecycles - Singleton, Transient, Per-Instance, and Per-Access patterns
• 🎯 Type-Safe - Full TypeScript support with decorator-based metadata
• 🔧 Flexible Scoping - Support for multiple isolated DI containers
• 🧪 Test-Friendly - Easy mocking and overriding for unit tests
• 📦 Extensible - Built on OOP/SOLID principles for easy customization

Installation

For the latest stable version:

npm i first-di

Quick Start

Prerequisites

Install reflect-metadata package and import it in your application entry point:

npm install reflect-metadata

Enable the following compiler options in tsconfig.json:

{
    "compilerOptions": {
        ...
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        ...
    }
}

Usage

Optional DI Mode

The simplest approach - write classes and inject dependencies through constructors. All dependencies are automatically resolved when calling resolve().

import { resolve, override, reflection } from "first-di";

@reflection // TypeScript will generate reflection metadata
class ProdRepository { // Default implementation

    public async getData (): Promise<string> {
        return Promise.resolve("production");
    }

}

@reflection
class MockRepository implements ProdRepository { // Mock implementation with same interface

    public async getData (): Promise<string> {
        return Promise.resolve("mock");
    }

}

@reflection
class ProdService {

    public constructor (
        private readonly prodRepository: ProdRepository
    ) { }

    public async getData (): Promise<string> {
        return this.prodRepository.getData();
    }

}

@reflection
class ProdStore {

    public constructor (
        // Inject dependency
        private readonly prodService: ProdService
    ) {
        // Other logic here
    }

    public async getData (): Promise<string> {
        return this.prodService.getData();
    }

}

if (process.env.NODE_ENV === "test") { // Override in test environment
    override(ProdRepository, MockRepository);
}

const store = resolve(ProdStore); // Create instance by framework
const data = await store.getData();

if (process.env.NODE_ENV === "test") {
    assert.strictEqual(data, "mock");
} else {
    assert.strictEqual(data, "production");
}

Classic DI Mode

For advanced scenarios, use abstract classes as contracts instead of interfaces. Abstract classes generate runtime metadata that TypeScript interfaces cannot provide.

import { resolve, override, reflection } from "first-di";

abstract class AbstractRepository { // Abstract instead of interface

    public abstract getData (): Promise<string>;

}

@reflection
class ProdRepository implements AbstractRepository {

    public async getData (): Promise<string> {
        return Promise.resolve("production");
    }

}

@reflection
class MockRepository implements AbstractRepository {

    public async getData (): Promise<string> {
        return Promise.resolve("mock");
    }

}

abstract class AbstractService { // Abstract instead of interface

    public abstract getData (): Promise<string>;

}

@reflection
class ProdService implements AbstractService {

    private readonly prodRepository: AbstractRepository;

    public constructor (prodRepository: AbstractRepository) {
        this.prodRepository = prodRepository;
    }

    public async getData (): Promise<string> {
        return this.prodRepository.getData();
    }

}

@reflection
class ProdStore {

    public constructor (
        private readonly prodService: AbstractService
    ) {}

    public async getData (): Promise<string> {
        return this.prodService.getData();
    }

}

override(AbstractService, ProdService);

if (process.env.NODE_ENV === "test") {
    override(AbstractRepository, MockRepository);
} else {
    override(AbstractRepository, ProdRepository);
}

const store = resolve(ProdStore);
const data = await store.getData();

if (process.env.NODE_ENV === "test") {
    assert.strictEqual(data, "mock");
} else {
    assert.strictEqual(data, "production");
}

Options

First DI has several points for customizing dependency options:

• Global - DI.defaultOptions: AutowiredOptions. Sets global default behavior.
• Override - override(fromClass, toClass, options?: AutowiredOptions). Sets behavior overridden dependency.
• Resolve - resolve(class, options?: AutowiredOptions). Sets behaviors for resolve dependencies.

Options have the following properties:

• lifeTime: AutowiredLifetimes - Sets lifeTime of dependency.

  SINGLETON - Create one instance for all resolvers.

  PER_INSTANCE - Create one instance for one resolver instance. Also called ‘transient’ or ‘factory’ in other containers.

  PER_OWNED - Create one instance for one type of resolver.

  PER_ACCESS - Create new instance on each access to resolved property.

Scopes

Support multiple scopes

import { DI } from "first-di";
import { ProductionService } from "../services/ProductionService";

const scopeA = new DI();
const scopeB = new DI();

const serviceScopeA = scopeA.resolve(ProductionService);
const dataA = await serviceScopeA.getData();

const serviceScopeB = scopeB.resolve(ProductionService);
const dataB = await serviceScopeB.getData();

API Reference

Core Functions

• override(fromClass, toClass, options?) - Override dependency resolution with custom implementation
• resolve(class, options?) - Resolve dependency with specified or default options
• singleton(class) - Resolve as singleton instance
• instance(class) - Always create new instance
• reset() - Clear all singletons and overrides (preserves global options)

Service Locator Pattern

The API functions can be used to implement the Service Locator pattern:

import { singleton, instance, resolve, AutowiredLifetimes } from "first-di";

class ApiDemo {

    private readonly service3: ApiService3 = resolve(ApiService3, { lifeTime: AutowiredLifetimes.PER_INSTANCE });

    private readonly service4: ApiService4 = singleton(ApiService4);

    private readonly service5: ApiService5 = instance(ApiService5);

}

Advanced Usage

Extending the DI Container

Built on OOP and SOLID principles, every component can be extended or customized:

import { DI } from "first-di";

class MyDI extends DI {
    // extended method
    public getAllSingletons(): IterableIterator<object> {
        return this.singletonsList.values();
    }
}

Contributing

Contributions are welcome! Please read our Contributing Guide and Code of Conduct before submitting pull requests.

License

MIT © Eugene Labutin