createStoreModule.js

import Vue from 'vue'

export default (api) => ({
  namespaced: true,
  state: {
    list: []
  },
  getters: {
    idxMap: state => state.list.reduce((map, { id }, i) => {
      map[id] = i
      return map
    }, {}),
    byId: (state, getters) => id => state.list[getters.idxMap[id]]
  },
  actions: {
    async all ({ state }) {
      if (state.list.length) {
        return state.list
      } else {
        const list = await api.get()
        state.list = list
        return list
      }
    },
    async one ({ getters }, id) {
      return getters.byId(id) || api.get(id)
    },
    async add ({ state }, item) {
      const newItem = await api.add(item)
      state.list.push(newItem)
      return newItem
    },
    async set ({ state, getters }, item) {
      const i = getters.idxMap[item.id]
      const newItem = await api.set(item)
      Vue.set(state.list, i, newItem)
      return newItem
    },
    async del ({ state, getters }, id) {
      const i = getters.idxMap[id]
      await api.del(id)
      Vue.delete(state.list, i)
      return state.list
    }
  }
})