store.js

const appModule = {
 state: initialState(),
  actions: {
    addUser ({commit, state}, user) {
      commit(types.ADD_USER, user)
    }
  },
  mutations: {
    [types.ADD_USER] (state, user) {
      state.users.push(user)
    }
  },
  getters: {
    users (state) {
      return state.users
    },
    usersLenght (state) {
      return state.users.length
    }
  } 
}