runtimer.js

function* runTimer(getState) {
  
  while(yield take('START')) {
    while(true) {
      const {stop, tick} = yield race({
        stop   : take('STOP'),
        tick : call(wait, ONE_SECOND);
      })
      if ( !stop ) {
        yield put(actions.tick());
      } else {
        break;
      }
    }
  }

}

You want to check for

if (!stop) { ... }

rather than

if (tick) { ... }

because

call(wait, ONE_SECOND)

returns undefined, causing you to break out of your loop on the first iteration.

@d4ncer thanks fixed

👍

I like this approach just that this if waist my brain. I don't like else

if ( stop ) {
break;
}
yield put(actions.tick());

I like @mrsoto's suggestion. A little one-liner is more readable:

if (stop) { break }
yield put(actions.tick())