在学习了之前的路由vue-router和状态管理vuex之后，就应该是网络交互了。就学习尤大推荐的axios了。刚好本人对网络请求这块除了会get、put、post和delete这四个方法之外知之甚少，刚好补全上。

注意：Vue官方推荐的网络通信库不再是vue-resource了，推荐使用axios。

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axios安装

npm:

$ npm install axios

bower:

$ bower install axios

Using cdn:

<script src="https://unpkg.com/axios/dist/axios.min.js"></script>

基本使用方法

GET请求

// Make a request for a user with a given ID
axios.get('/user?ID=12345')
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

// Optionally the request above could also be done as
axios.get('/user', {
    params: {
      ID: 12345
    }
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

POST请求

 axios.post('/user', {
    firstName: 'Fred',
    lastName: 'Flintstone'
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

同时执行多个请求

function getUserAccount() {
  return axios.get('/user/12345');
}

function getUserPermissions() {
  return axios.get('/user/12345/permissions');
}

axios.all([getUserAccount(), getUserPermissions()])
  .then(axios.spread(function (acct, perms) {
    // Both requests are now complete
  }));

其实和其他的ajax库一样，基本用法都是差不多的。大家一看就知道怎么用。

axios API

可以直接通过config来完成请求
axios(config)

axios({
  method: 'post',
  url: '/user/12345',
  data: {
    firstName: 'Fred',
    lastName: 'Flintstone'
  }
});

axios(url, [config])

// Send a GET request (default method)
axios('/user/12345');

请求方法别名

下面是axios支持的所有请求方法别名，便于各种请求。
注：[...]中的数据表示可以为空。url是ajax请求地址；data是提交的数据对象；config是配置对象，所有ajax配置都可以在config中实现。

• axios.request(config)
• axios.get(url[, config])
• axios.delete(url[, config])
• axios.head(url[, config])
• axios.post(url[, data[, config]])
• axios.put(url[, data[, config]])
• axios.patch(url[, data[, config]])

并发性

下列接口用于处理并发请求(同时处理多个多个request)

• axios.all(iterable)
• axios.spread(callback)

axios实例

可以用自定义的config创建一个axios实例
axios.create([config])

var instance = axios.create({
  baseURL: 'https://some-domain.com/api/',
  timeout: 1000,
  headers: {'X-Custom-Header': 'foobar'}
});

实例方法

下面是实例的所有可用方法，方法中的config会与axios实例中的config合并。（实例可以将一些通用的config先配置好）

• axios#request(config)
• axios#get(url, [config])
• axios#delete(url, [config])
• axios#head(url, [config])
• axios#post(url[, data[, config]])
• axios#put(url[, data[, config]])
• axios#patch(url[, data[, config]])

Config

重点来了，来看看Config。
下面列出了config的所有配置项，其中之后url是必填的。当method没有指定方法，默认为GET。

{
  // `url` is the server URL that will be used for the request
  // 用来向服务器发送请求的url
  url: '/user',

  // `method` is the request method to be used when making the request
 // 请求方法
  method: 'get', // default

  // `baseURL` will be prepended to `url` unless `url` is absolute.
  // It can be convenient to set `baseURL` for an instance of axios to pass relative URLs
  // to methods of that instance.
  // 假如`url`不是绝对路径，那么向服务器发送请求的URL将是`baseURL + url`
  baseURL: 'https://some-domain.com/api/',

  // `transformRequest` allows changes to the request data before it is sent to the server
  // This is only applicable for request methods 'PUT', 'POST', and 'PATCH'
  // The last function in the array must return a string, an ArrayBuffer, or a Stream
  transformRequest: [function (data) {
    // Do whatever you want to transform the data

    return data;
  }],

  // `transformResponse` allows changes to the response data to be made before
  // it is passed to then/catch
  transformResponse: [function (data) {
    // Do whatever you want to transform the data

    return data;
  }],

  // `headers` are custom headers to be sent
  headers: {'X-Requested-With': 'XMLHttpRequest'},

  // `params` are the URL parameters to be sent with the request
  // Must be a plain object or a URLSearchParams object
  params: {
    ID: 12345
  },

  // `paramsSerializer` is an optional function in charge of serializing `params`
  // (e.g. https://www.npmjs.com/package/qs, http://api.jquery.com/jquery.param/)
  paramsSerializer: function(params) {
    return Qs.stringify(params, {arrayFormat: 'brackets'})
  },

  // `data` is the data to be sent as the request body
  // Only applicable for request methods 'PUT', 'POST', and 'PATCH'
  // When no `transformRequest` is set, must be of one of the following types:
  // - string, plain object, ArrayBuffer, ArrayBufferView, URLSearchParams
  // - Browser only: FormData, File, Blob
  // - Node only: Stream
  data: {
    firstName: 'Fred'
  },

  // `timeout` specifies the number of milliseconds before the request times out.
  // If the request takes longer than `timeout`, the request will be aborted.
  timeout: 1000,

  // `withCredentials` indicates whether or not cross-site Access-Control requests
  // should be made using credentials
  withCredentials: false, // default

  // `adapter` allows custom handling of requests which makes testing easier.
  // Return a promise and supply a valid response (see [response docs](#response-api)).
  adapter: function (config) {
    /* ... */
  },

  // `auth` indicates that HTTP Basic auth should be used, and supplies credentials.
  // This will set an `Authorization` header, overwriting any existing
  // `Authorization` custom headers you have set using `headers`.
  auth: {
    username: 'janedoe',
    password: 's00pers3cret'
  },

  // `responseType` indicates the type of data that the server will respond with
  // options are 'arraybuffer', 'blob', 'document', 'json', 'text', 'stream'
  responseType: 'json', // default

  // `xsrfCookieName` is the name of the cookie to use as a value for xsrf token
  xsrfCookieName: 'XSRF-TOKEN', // default

  // `xsrfHeaderName` is the name of the http header that carries the xsrf token value
  xsrfHeaderName: 'X-XSRF-TOKEN', // default

  // `onUploadProgress` allows handling of progress events for uploads
  onUploadProgress: function (progressEvent) {
    // Do whatever you want with the native progress event
  },

  // `onDownloadProgress` allows handling of progress events for downloads
  onDownloadProgress: function (progressEvent) {
    // Do whatever you want with the native progress event
  },

  // `maxContentLength` defines the max size of the http response content allowed
  maxContentLength: 2000,

  // `validateStatus` defines whether to resolve or reject the promise for a given
  // HTTP response status code. If `validateStatus` returns `true` (or is set to `null`
  // or `undefined`), the promise will be resolved; otherwise, the promise will be
  // rejected.
  validateStatus: function (status) {
    return status >= 200 && status < 300; // default
  },

  // `maxRedirects` defines the maximum number of redirects to follow in node.js.
  // If set to 0, no redirects will be followed.
  maxRedirects: 5, // default

  // `httpAgent` and `httpsAgent` define a custom agent to be used when performing http
  // and https requests, respectively, in node.js. This allows to configure options like
  // `keepAlive` that are not enabled by default.
  httpAgent: new http.Agent({ keepAlive: true }),
  httpsAgent: new https.Agent({ keepAlive: true }),

  // 'proxy' defines the hostname and port of the proxy server
  // `auth` indicates that HTTP Basic auth should be used to connect to the proxy, and supplies credentials.
  // This will set an `Proxy-Authorization` header, overwriting any existing `Proxy-Authorization` custom headers you have set using `headers`.
  proxy: {
    host: '127.0.0.1',
    port: 9000,
    auth: : {
      username: 'mikeymike',
      password: 'rapunz3l'
    }
  },

  // `cancelToken` specifies a cancel token that can be used to cancel the request
  // (see Cancellation section below for details)
  cancelToken: new CancelToken(function (cancel) {
  })
}

分析Config

配置参数很多，我们一个一个来了解它们

• url —— 用来向服务器发送请求的url
• method —— 请求方法，默认是GET方法
• baseURL —— 基础URL路径，假如url不是绝对路径，如https://some-domain.com/api/v1/login?name=jack,那么向服务器发送请求的URL将会是baseURL + url。
• transformRequest —— transformRequest方法允许在请求发送到服务器之前修改该请求，此方法只适用于PUT、POST和PATCH方法中。而且，此方法最后必须返回一个string、ArrayBuffer或者Stream。
• transformResponse —— transformResponse方法允许在数据传递到then/catch之前修改response数据。此方法最后也要返回数据。
• headers —— 发送自定义Headers头文件，头文件中包含了http请求的各种信息。
• params —— params是发送请求的查询参数对象，对象中的数据会被拼接成url?param1=value1&param2=value2。
• paramsSerializer —— params参数序列化器。
• data —— data是在发送POST、PUT或者PATCH请求的数据对象。
• timeout —— 请求超时设置，单位为毫秒
• withCredentials —— 表明是否有跨域请求需要用到证书
• adapter —— adapter允许用户处理更易于测试的请求。返回一个Promise和一个有效的response
• auth —— auth表明提供凭证用于完成http的身份验证。这将会在headers中设置一个Authorization授权信息。自定义Authorization授权要设置在headers中。
• responseType —— 表示服务器将返回响应的数据类型，有arraybuffer、blob、document、json、text、stream这6个类型，默认是json类似数据。
• xsrfCookieName —— 用作 xsrf token 值的 cookie 名称
• xsrfHeaderName —— 带有 xsrf token 值 http head 名称
• onUploadProgress —— 允许在上传过程中的做一些操作
• onDownloadProgress —— 允许在下载过程中的做一些操作
• maxContentLength —— 定义了接收到的response响应数据的最大长度。
• validateStatus —— validateStatus定义了根据HTTP响应状态码决定是否接收或拒绝获取到的promise。如果 validateStatus 返回 true (或设置为 null 或 undefined ),promise将被接收;否则,promise将被拒绝。
• maxRedirects —— maxRedirects定义了在node.js中redirect的最大值，如果设置为0，则没有redirect。
• httpAgent —— 定义在使用http请求时的代理
• httpsAgent —— 定义在使用https请求时的代理
• proxy —— proxy定义代理服务器的主机名和端口，auth
• cancelToken —— cancelToken定义一个 cancel token 用于取消请求

Response

当我们ajax获取数据成功后会返回一个response对象，它包含了以下内容：

{
  // `data` is the response that was provided by the server
  data: {},

  // `status` is the HTTP status code from the server response
  status: 200,

  // `statusText` is the HTTP status message from the server response
  statusText: 'OK',

  // `headers` the headers that the server responded with
  headers: {},

  // `config` is the config that was provided to `axios` for the request
  config: {}
}

response是通过promise的then方法来获取,具体使用方法如下：

axios.get('/user/12345')
  .then(function(response) {
    console.log(response.data);
    console.log(response.status);
    console.log(response.statusText);
    console.log(response.headers);
    console.log(response.config);
  });

相对的，我们有时也会出现ajax报错，此时就会到我们的catch中去捕获异常error对象。

为何放弃vue-resource

尤大的原话：

最近团队讨论了一下，Ajax 本身跟 Vue 并没有什么需要特别整合的地方，使用 fetch polyfill 或是 axios、superagent 等等都可以起到同等的效果，vue-resource 提供的价值和其维护成本相比并不划算，所以决定在不久以后取消对 vue-resource 的官方推荐。已有的用户可以继续使用，但以后不再把 vue-resource 作为官方的 ajax 方案。
知乎链接：https://www.zhihu.com/question/52418455/answer/130535375