`holdOrResumeSingleCall` will be a no op when `CallScreen.incomingContainer.classList.contains('displayed')` so I think the code will be much clearer by having 2 distinct early returns.

```
    if (CallScreen.incomingContainer.classList.contains('displayed')) {
      return;
    }

    if (handledCalls.length < 2) {
      holdOrResumeSingleCall();
      return;
    }

```