store.js
const state = {

userPermission: [],

}
const getters = {

getUserPermission: state => state.userPermission,

}
const mutations = {

userPermission(state,userPermission){
    localStorage.userPermission = JSON.stringify(userPermission)
    state.userPermission = localStorage.userPermission
}

}
const actions = {

userPermission({commit},userPermission){
    return new Promise(function(resolve,reject){
        commit('userPermission',userPermission)
    })
}

}

export default{

state,
getters,
mutations,
actions

}
组件中
import {mapState} from "vuex"
computed: mapState({

userPermission(state){
alert(1)//这里进不来是为什么？？？？？我这写法错了吗？
let userPermission = JSON.parse(localStorage.getItem('getUserPermission'))
if(state.userPermission.length === 0){
    return 
}
return state.userPermission
}

})
第一次使用，望指教