vue报错TypeError: Cannot read property 'protocol' of undefined

错误信息如下所示：

isURLSameOrigin.js?3934:57 Uncaught (in promise) TypeError: Cannot read property 'protocol' of undefined
    at isURLSameOrigin (isURLSameOrigin.js?3934:57)
    at dispatchXhrRequest (xhr.js?b50d:103)
    at new Promise (<anonymous>)
    at xhrAdapter (xhr.js?b50d:11)
    at dispatchRequest (dispatchRequest.js?5270:59)

问题代码，查看根目录main.js中引入axios的代码，是否如下所示：

import axios from 'axios'
import qs from 'qs'

Vue.use(axios)

正确写法：

import axios from 'axios'
import qs from 'qs'

Vue.prototype.axios = axios