webpack-bootstrap-ui-kit/src/js/store/reducers/counter.js

export default function counter(
  state = {
    value: 0,
  },
  action
) {
  switch (action.type) {
    case "counter/incremented":
      return {
        value: state.value + 1,
      };
    case "counter/decremented":
      return {
        value: state.value - 1,
      };
    default:
      return state;
  }
}