Simple dependency injection library for TypeScript

This is inspired by Angular's inject() function, and doesn't rely on decorators. The dependency resolution is done purely at run time.

It currently only supports injecting classes

Installation

deno add jsr:@silvo38/inject

Usage

import { inject, provide } from "jsr:@silvo38/inject";

class Foo {
  // Inject fields directly.
  private readonly someDepA = inject(SomeDepA);
  private readonly someDepB = inject(SomeDepB);
}

// Provide a class with a no-args constructor.
provide(Foo);

// Provide a specific instance that you have constructed manually.
const someDepA = SomeDepA.complexFactory();
provide(SomeDepA, someDepA);

// Provide an instance via a factory function. You can call inject() here.
provide(SomeDepB, () => new SomeDepB("someArg", inject(SomeDepA), "otherArg"));

Unit testing

There is a single global injector instance, so for unit testing you will need to call resetGlobalInjector() to clear any existing providers. Otherwise, usage in unit tests is the same as in production.

import { inject, provide, resetGlobalInjector } from "jsr:@silvo38/inject";

describe("Test something", () => {
  beforeEach(() => {
    resetGlobalInjector();

    provide(SomeDepA, new FakeDepA());
    // Provide other deps.
  });

  it("should do something", () => {
    const foo = inject(Foo);
    // Do something with foo.
  });
});