说明两点：
interceptor必须在请求前设置才有效。
直接为axios全局对象创建interceptor，会导致全局的axios发出的请求或接收的响应都会被拦截到，所以应该使用axios.create()来创建单独的axios实例。
官方原话：
You can add interceptors to a custom instance of axios.
var instance = axios.create();
instance.interceptors.request.use(function () {/*...*/});
用vue-cli创建了个测试项目，代码如下：
Hello.vue
<script>
import axios from 'axios'
export default {
name: 'hello',
data () {
return {
msg: 'Welcome to Your Vue.js App'
}
},
methods: {
getImg () {
axios.get('
https://static.segmentfault.com/v-595f50ca/global/img/logo-b.svg')
.then((response) => {
console.log(response)
}).catch((error) => {
console.log(error)
})
},
addInterceptors () {
axios.interceptors.request.use(function (config) {
// Do something before request is sent
console.log('开始请求')
console.log(`请求地址: ${config.url}`)
return config
}, function (error) {
// Do something with request error
console.log('请求失败')
return Promise.reject(error)
})
axios.interceptors.response.use(function (config) {
// Do something before request is sent
console.log('接收响应')
return config
}, function (error) {
// Do something with request error
console.log('响应出错')
return Promise.reject(error)
})
}
},
mounted () {
this.addInterceptors()
this.getImg()
}
}
</script>