vue用axios时报错：Cannot read property 'protocol' of undefined！

import  Vue  from 'vue'
import Vuex from 'vuex'
import axios from 'axios'

Vue.use(Vuex)
Vue.use(axios)

报错信息：

isURLSameOrigin.js?cf95:57 Uncaught (in promise) TypeError: Cannot
read property 'protocol' of undefined

at isURLSameOrigin (eval at <anonymous> (app.js:929), <anonymous>:57:21)
at dispatchXhrRequest (eval at <anonymous> (app.js:754), <anonymous>:108:50)
at Promise (<anonymous>)
at xhrAdapter (eval at <anonymous> (app.js:754), <anonymous>:12:10)
at dispatchRequest (eval at <anonymous> (app.js:866), <anonymous>:52:10)
报错截图：

但是:通过原型式使用就正常了：

import Vue from 'vue'
import Vuex from 'vuex'
import axios from 'axios'

Vue.use(Vuex)
Vue.prototype.$ajax = axios