Pinia plain JavaScript inheritance

store.js

function baseCounterStore(options) {
  const baseState = {
    counter: 0
  }

  const newState = options.state
  options.state = () => {
    return {
      ...baseState,
      ...newState()
    }
  }

  options.getters = {
    ...options.getters,
    doubleCounter: (state) => {
      return state.counter * 2
    }
  }

  return options
}

export const useShoppingCartStore = defineStore(
  baseCounterStore({
    id: 'shopping-cart',
    state: () => ({}),
    getters: {}
  })
)