Please don't use dependency injection frameworks in modern Typescript/Javascript

please_dont_use_di.js

/*
If you are using dependency injection in Typescript/Javascript under the pretense that
you are doing anything other than overengineering and making your life and your team's life 
harder, please read this.
*/

// The code below doesn't care what `logger` is, only that it exports `log`!
// This creates a test seam / interface behind which you can replace it with ANYTHING!
// You only care that the thing being exported has a `log` function!
import { log } from './logger'

// The code below doesn't care what `db` is, only that it exports `exec`!
import { exec } from './db' 

const saveRecord = () => {
  exec("update widgets etc...")
  log("did the thing")
}

// some things `exec` could be...
// export const exec = (sql) => {
//   doARealDbThing(sql)
// }

// export const exec = (sql) => {
//   doAMockedDbThing(sql)
// }

// export const exec = (sql) => {
//   if (someCondition) {
//     doARealDbThing(sql)
//   } else {
//     doAMockedDbThing(sql)
//   }
// }

// jest.mock('./exec) // Hey, look, Jest does this too without constuctor-injection

/*

Note that I never:

* Pushed all dependencies in via constructor
* Used a class as a module container (or at all)
* Had to create several layers of dependency injection configuration
* Imported any exotic dependencies to replace ES6 import/export

Typescript/Javascript isn't Java or C#!

Angular and NestJS and anything else doing DI in javascript/typescript is unnecessary.
They are reinventing an additional module system on top of ES6's module system.
This might have been more helpful back before es2015, but it's been 6 years; it's time to let it go.

Programming is hard enough without making things harder for no real gain.

Pass it on.

*/