branneman

{
  // Tight coupling from A to B  => A needs B to be defined, callable and adhere to an interface
  // No coupling from B to A     => B does not need A in any way (pure fn)
  function a() {
    b()
  }
  function b() {}
}

{

Lucifier129

import { interval, isObservable } from 'rxjs'
import { tap } from 'rxjs/operators'

const type = {
  isThenable: obj => !!(obj && typeof obj.then === 'function'),
  isObservable: obj => !!(obj && isObservable(obj)),
  isError: obj => obj instanceof Error,
  isObject: obj => obj != null && typeof obj === 'object'
}