[🔷TS -- Simple dependency injection] #TypeScript

simple_di.ts

import { foo } from '../libs/foo'
import { bar } from './libs/bar'

interface InjectableDependencies {
    logger: Console
    foo: typeof foo
}

const defaultDependencies: InjectableDependencies = {
    logger: console,
    foo,
}

async function factory(dependencies: Partial<InjectableDependencies> = {}) {
    const { foo, logger } = Object.assign({}, defaultDependencies, dependencies)

    logger.log('Hello')
  
    function doStuff(x): Promise<void> {
        return foo().then(x => bar(x))
    }

    return {
        doStuff,
    }
}

// optional
const defaultInstance = factory()
const doStuff = defaultInstance.doStuff

export {
    InjectableDependencies,
    factory,
    doStuff,
}