Getting started

Installation

Just install it using your favorite package manager.

Needle DI is published to NPM and JSR, and is also compatible with Deno.

npm

npm install @needle-di/core

yarn

yarn add @needle-di/core

pnpm

pnpm install @needle-di/core

deno

deno add jsr:@needle-di/core

Transpiler settings

Needle DI uses native ECMAScript decorators, which are currently in stage 3 of the TC39 standardization process.

If you're using Deno, you can run your code as-is. However, when running on Node.js or in a browser, you might need to transpile your code first, as your runtime might not have implemented it yet.

Make sure to use ES2022 or lower as target:

tsc (tsconfig.json)

{
  "compilerOptions": {
    "target": "ES2022"
  }
}

vite (vite.config.mjs)

export default defineConfig({
  esbuild: {
    target: 'es2022',
    // ...
  },
  // ...
});

esbuild

esbuild app.js --target=es2022

Basic example

Here’s a simple example using constructor injection to inject one service into another.

import { injectable, inject } from "@needle-di/core";

@injectable()
class FooService {
    // ...
}

@injectable()
class BarService {
  constructor(private fooService = inject(FooService)) {}
}

As you can see, Needle DI uses default parameter values for constructor injection.

The @injectable decorator eliminates the need to register services manually.

Bootstrapping

To bootstrap the BarService, you have to create a new dependency injection container, and use the .get() method on it to retrieve it by its token:

import { injectable, inject, Container } from "@needle-di/core";
import { BarService } from "./bar.service";

const container = new Container();

// you can use container.bind() to register more services.

const barService = container.get(BarService);

That's it!

What's next?

Learn how you can use binding to register services.