Extremely thin, async dependency injection, now with a getting started guide.
Inspired by Google's Guice library and written in Typescript.
- async dependency resolution
- constructor and property injection
- modular containers with inheritance
- named dependencies using strings or unique symbols
- typed errors
- typescript typedefs
- zero runtime dependencies, bundled or otherwise
- extensive test coverage
- 3.x versions are compatible with Node 12+
- 4.x versions are compatible with Node 16+
Consider a Server class that needs to fetch data from the Cache and Filesystem, but doesn't know (or need to
know) how those are implemented. The following example is also part of the unit tests.
import { LocalModule } from './local';
import { NetworkModule } from './network';
class Cache {
public get(path: string, ttl: number, fallback: () => Promise<string>): Promise<string> {
/* ... */
}
}
class Filesystem {
public get(path: string): Promise<string> {
/* ... */
}
}
/**
* Constructors, strings, and symbols are supported. Symbols are
* preferred, as the most unique, but names can be convenient.
*/
@Inject(Cache.name.toLowerCase(), Filesystem.name.toLowerCase())
class Server {
protected readonly cache: Cache;
protected readonly filesystem: Filesystem;
protected readonly ttl: number;
constructor(options) {
this.cache = options.cache;
this.filesystem = options.filesystem;
this.ttl = defaultTo(options.ttl, 0);
}
get(path: string) {
return options.cache.get(path, this.ttl, () => options.filesystem.get(path));
}
}
const TEST_TTL = 60;
function module() {
if (process.env['DEBUG'] === 'TRUE') {
return new LocalModule();
} else {
return new NetworkModule();
}
}
async function main() {
const container = Container.from(module());
await container.configure();
const server = await container.create(Server, {
/* cache and filesystem are found and injected by container */
ttl: TEST_TTL,
});
/* server.cache.get and server.filesystem.get will be called in order */
const result = await server.get('some/file');
}noicejs will collect dependencies from the decorated constructor and any superclasses, find a provider for each injected dependency, and asynchronously resolve them before calling the constructor. Any extra parameters are passed on to the original constructor, along with the container and resolved dependencies.
To build a bundle and run tests:
> make
yarn
yarn install v1.17.3
[1/4] Resolving packages...
success Already up-to-date.
Done in 0.20s.
/home/ssube/code/ssube/noicejs//node_modules/.bin/rollup --config /home/ssube/code/ssube/noicejs//config/rollup.js
src/index.ts, test/harness.ts, test/**/Test*.ts → out/...
...
created out/ in 3.3s
/home/ssube/code/ssube/noicejs//node_modules/.bin/api-extractor run --config /home/ssube/code/ssube/noicejs//config/api-extractor.json --local -v
api-extractor 7.3.8 - https://api-extractor.com/
...
API Extractor completed successfully
Success!