// scoreboard-reducer.js
const INITIAL_STATE = {
  home: 0,
  away: 0,
}

export const scoreboardReducer = (state = INITIAL_STATE, action) {
  switch (action.type) {
    case 'INCREMENT_SCORE':
      const scoringSide = action.payload.team;
      return {...state, [scoringSide]: state.[scoringSide] + 1 };
    default:
      return state;
  }
}

// Some container component
export class Game extends React.Component {
  ...
  onGoalScored(scoringTeam) {
    this.props.dispatch({type: 'INCREMENT_SCORE', team: scoringTeam}
  }
}