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This package works with Cloudflare Workers, Node.js, Deno, Bun, Browsers
This package works with Cloudflare Workers
This package works with Node.js
This package works with Deno
This package works with Bun
This package works with Browsers
JSR Score
70%
Published
a week ago (2.0.2)

Codecov

Injector

A lightweight, type-aware dependency injection container for JavaScript/TypeScript (with JSDoc support), supporting class and function dependencies with type inference.

Features

  • Type Inference: Automatically infers dependency types
  • Class & Function Support: Register instances from classes or factory functions
  • Error Handling: Throws clear errors for unregistered dependencies
  • Zero Dependencies: Tiny footprint (< 1KB minified)

Installation

npm install "@collidor/injector"

Usage

Basic Class Example

import { Injector } from '"@collidor/injector"';

// Create injector
const injector = new Injector();

// Register a class instance
class DatabaseService {
  connect() { return 'Connected!'; }
}

injector.register(DatabaseService, new DatabaseService());

// Inject the instance (type inferred as DatabaseService)
const db = injector.inject(DatabaseService);
console.log(db.connect()); // "Connected!"

Function Dependency Example

// Register a factory function
const configFactory = () => ({ env: 'production' });
injector.register(configFactory, configFactory());

// Inject the function result (type inferred as { env: string })
const config = injector.inject(configFactory);
console.log(config.env); // "production"

Register in class properties:

import {Database} from './database.ts'

class Service {
    private database = inject(Database)

    getData() {
        return this.database.query();
    }
}

Interdenpendency or race condition

If two classes depend on each other in any place except the constructor, we can use getters or get the instances directly in the Methods:

import {Database} from './database.ts'

class Service {
    get database(): Database {
        return inject(Database);
    }

    getData() {
        return this.database.query();
    }
}

Error Handling

try {
  injector.inject(UnregisteredService); // Throws error
} catch (err) {
  console.error(err.message); // "No instance registered for type: UnregisteredService"
}

API

Injector

register(type, instance)

  • Parameters:
    • type: Constructor | Function | Symbol | Object (dependency identifier)
    • instance: Value to store
  • Returns: void

Registers a dependency instance.

inject(type)

  • Parameters:
    • type: Constructor | Function | Symbol | Object (dependency identifier)
  • Returns:
    T extends Type<infer M> ? M : T extends (...args: any[]) => infer R ? R : any
    
  • Throws: Error if no instance is registered for type

Retrieves a dependency instance.

Type Inference

Works with both class constructors and factory functions:

// Class registration
class AuthService {
  login() { /* ... */ }
}
injector.register(AuthService, new AuthService());
const auth = injector.inject(AuthService); // Inferred as AuthService

// Function registration
const loggerFactory = () => ({ log: (msg: string) => console.log(msg) });
injector.register(loggerFactory, loggerFactory());
const logger = injector.inject(loggerFactory); // Inferred as { log: (msg: string) => void }

Contributing

  1. Fork the repository
  2. Create a feature branch
  3. Submit a pull request

License

MIT

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Add Package

deno add jsr:@collidor/injector

Import symbol

import * as injector from "@collidor/injector";

---- OR ----

Import directly with a jsr specifier

import * as injector from "jsr:@collidor/injector";

Add Package

npx jsr add @collidor/injector

Import symbol

import * as injector from "@collidor/injector";

Add Package

yarn dlx jsr add @collidor/injector

Import symbol

import * as injector from "@collidor/injector";

Add Package

pnpm dlx jsr add @collidor/injector

Import symbol

import * as injector from "@collidor/injector";

Add Package

bunx jsr add @collidor/injector

Import symbol

import * as injector from "@collidor/injector";