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 ECMAScript stage 3 decorators.

If you're using Deno, you can run your code as-is. However, when using Node.js or a browser as runtime, you will need to transpile your code first, since decorators are not yet supported.

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)) {}
  //                  ^? Type will be inferred as `FooService`
}

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

The @injectable decorator eliminates the need to register services manually. To construct the BarService, you have to create a dependency injection container, and use the container.get() method:

import { Container } from "@needle-di/core";

const container = new Container();
const barService = container.get(BarService);
//    ^? Type will be inferred as `BarService`

That's it!

What's next?

Check out the concepts to learn more and see more examples.