feat: add init options when plugin installed

Author: yugasun

README.md

@@ -29,50 +29,101 @@ And in your entry file:
 import Vue from 'Vue'
 import VueAxiosPlugin from 'vue-axios-plugin'
 
-const checkStatus = (response) => {
-  if(response.status === 404){
-    // do something
-  }
-  if(response.status === 500){
-    //do something
-  }
-
-  // after your uniform request handler, you must return response
-  return response
-}
-
 Vue.use(VueAxiosPlugin, {
-  checkStatus: checkStatus
+  // request interceptor handler
+  reqHandleFunc: config => config,
+  reqErrorFunc: error => Promise.reject(error),
+  // response interceptor handler
+  resHandleFunc: response => response,
+  resErrorFunc: error => Promise.reject(error)
 })
 ```
 
+## Options
+
+Except axios default [request options](https://github.com/axios/axios#request-config), `vue-axios-plugin` provide below request/response interceptors options:
+
+|Name|Type|Default|Description|
+|:--:|:--:|:-----:|:----------|
+|**[`reqHandleFunc`](#)**|`{Function}`|`config => config`|The handler function for request, before request is sent|
+|**[`reqErrorFunc`](#)**|`{Function}`|`error => Promise.reject(error)`|The error function for request error|
+|**[`resHandleFunc`](#)**|`{Function}`|`response => response`|The handler function for response data|
+|**[`resErrorFunc`](#)**|`{Function}`|`error => Promise.reject(error)`| The error function for response error |
+
 ## Usage
 
-default method in `$http` :
+default method in `$http`, it just contains get and post method:
 
 ```javascript
 this.$http.get(url, data, options).then((response) => {
-  console.log(response.data)
+  console.log(response)
 })
 this.$http.post(url, data, options).then((response) => {
-  console.log(response.data)
+  console.log(response)
 })
 ```
 
-use axios original method in `$axios`
+use axios original method in `$axios`, by this, you can use all allowed http methods: get,post,delete,put...
 
 ```javascript
-this.$axios.get(url).then((response) => {
-  console.log(response.data)
+this.$axios.get(url, data, options).then((response) => {
+  console.log(response)
+})
+
+this.$axios.post(url, data, options).then((response) => {
+  console.log(response)
 })
+```
+
+## Notice!!!
 
+When you send a request use `application/x-www-form-urlencoded` format, you need to use [qs]() library to transform post data, like below:
+
+```js
 import qs from 'qs'
-this.$axios.post(url, qs.stringify(data).then((response) => {
-  console.log(response.data)
+this.$http.post(url, qs.stringify(data), {
+  headers: {
+    'Content-Type': 'application/x-www-form-urlencoded',
+  }
+}).then((response) => {
+  console.log(response)
+})
+```
+
+But if the `data` has properties who's type if object/array, you need convert these properties into JSON string:
+
+```js
+import qs from 'qs'
+
+function jsonProp (obj) {
+  // type check
+  if (!obj || (typeof obj !== 'object')) {
+    return obj
+  }
+  Object.keys(obj).forEach((key) => {
+    if ((typeof obj[key]) === 'object') {
+      obj[key] = JSON.stringify(obj[key])
+    }
+  })
+  return obj
+}
+
+this.$http.post(url, qs.stringify(data), {
+  headers: {
+    'Content-Type': 'application/x-www-form-urlencoded',
+  },
+  transformRequest: [
+    function (data) {
+      // if data has object type properties, need JSON.stringify them.
+      return qs.stringify(jsonProp(data))
+    }
+  ]
+}).then((response) => {
+  console.log(response)
 })
 ```
 
-More usage, go to [axios](https://github.com/mzabriskie/axios)
+More usage, view [axios](https://github.com/mzabriskie/axios)
 
 ## License