How to solve this basic ES6-module circular dependency problem?

[Mikael Sand]

How about applying Inversion of Control by implementing Dependency 
Injection using Constructor injection? Just make your C constructor take 
two parameters A and B like this:

```js
// --- Module A

import C from './C';

export default class A extends C {
     // ...
}

// --- Module B

import C from './C';

export default class B extends C {
     // ...
}

// --- Module C

export default class C {
     constructor(A, B) {
         // this may run later, after all three modules are evaluated, or
         // possibly never.
         console.log(A);
         console.log(B);
     }
}

// --- Entrypoint

import A from './A';
import B from './B';
import C from './C';
const c = new C(A, B);
console.log('Entrypoint', C, c);
document.getElementById('out').textContent = 'Entrypoint ' + C + ' ' + c;
```

https://www.webpackbin.com/bins/-KlDeP9Rb60MehsCMa8u

https://en.wikipedia.org/wiki/Dependency_injection#Constructor_injection

https://en.wikipedia.org/wiki/Inversion_of_control#Implementation_techniques