axios深入/源码分析/拦截器原理/该对象既可以当对象使用，也可以当函数使用; 任何的发送请求都是有 request方式执行

axios

是基于promise 运行在browser和node环境

基本使用

 const btns = document.querySelectorAll("button");
    btns[1].onclick = function() {
        axios({
            method:"POST",
            url:"https:/xxx/list",
         
            data:{
                owId:"2"
            }
        }).then(res =>  {
            console.log(res);
        })
    }
    btns[0].onclick = function() {
        axios({
            method:"Get",
            url:"https://xxx/list",
        
            params:{
                owId:"2"
            }
        }).then(res =>  {
            console.log(res);
        })
    }

其他使用方法

axios.request({
    method:"POST",
    url:"https://xxx/list",
    data:{
        Id:"2"
    }
}).then(res => {
    console.log(res);
})

axios.post("https://xxx/list",{Id:"2"}).then(res => {
    
})
axios.get("https://xxx/list",{params:{Id:"2"}}).then(res => {
    
})

resquest配置对象

{
  // 请求目标路径
  url: '/user',

  // 请求的方法
  method: 'get', // default

  //请求根路径
  baseURL: 'https://some-domain.com/api/',

  //发送请求前先将数据进行处理，处理后的数据返回给后台
  transformRequest: [function (data, headers) {
    // Do whatever you want to transform the data

    return data;
  }],

  //响应后结果进行处理
  transformResponse: [function (data) {
    // Do whatever you want to transform the data

    return data;
  }],

  // 请求头信息： 如果在头部加入 校验信息
  headers: {'X-Requested-With': 'XMLHttpRequest'},


  // 设置url参数，可以通过对象设置，可以替代：xxx/id=12345
  params: {
    ID: 12345
  },

  // 参数序列化，转换成字符串， 
  // (e.g. https://www.npmjs.com/package/qs, http://api.jquery.com/jquery.param/)
  paramsSerializer: function (params) {
    return Qs.stringify(params, {arrayFormat: 'brackets'})
  },

  // form表单提交参数
  data: {
    firstName: 'Fred'
  },
  
  // syntax alternative to send data into the body
  // method post
  // only the value is sent, not the key
  data: 'Country=Brasil&City=Belo Horizonte',

  //请求超时时间.
  timeout: 1000, // default is `0` (no timeout)

  //跨域请求，对cookie是否跨域，如果 true,跨域会携带cookie
  withCredentials: false, // default

  // 请求适配器
  // Return a promise and supply a valid response (see lib/adapters/README.md).
  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`.
  // Please note that only HTTP Basic auth is configurable through this parameter.
  // For Bearer tokens and such, use `Authorization` custom headers instead.
  //请求基础验证
  auth: {
    username: 'janedoe',
    password: 's00pers3cret'
  },

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

  // `responseEncoding` indicates encoding to use for decoding responses (Node.js only)
  // Note: Ignored for `responseType` of 'stream' or client-side requests
  //响应编码
  responseEncoding: 'utf8', // default

  // `xsrfCookieName` is the name of the cookie to use as a value for xsrf token
  //做请求保护，携带标识
  xsrfCookieName: 'XSRF-TOKEN', // default

  // `xsrfHeaderName` is the name of the http header that carries the xsrf token value
  //做请求保护，携带标识 
  xsrfHeaderName: 'X-XSRF-TOKEN', // default

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

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

  // `maxContentLength` defines the max size of the http response content in bytes allowed in node.js
  //响应体的最大尺寸
  maxContentLength: 2000,

  // `maxBodyLength` (Node only option) defines the max size of the http request content in bytes allowed
 //响应体的最大尺寸
  maxBodyLength: 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.
  //对成功状态
  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

  // `socketPath` defines a UNIX Socket to be used in node.js.
  // e.g. '/var/run/docker.sock' to send requests to the docker daemon.
  // Only either `socketPath` or `proxy` can be specified.
  // If both are specified, `socketPath` is used.
  socketPath: null, // default

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

  // `proxy` defines the hostname, port, and protocol of the proxy server.
  // You can also define your proxy using the conventional `http_proxy` and
  // `https_proxy` environment variables. If you are using environment variables
  // for your proxy configuration, you can also define a `no_proxy` environment
  // variable as a comma-separated list of domains that should not be proxied.
  // Use `false` to disable proxies, ignoring environment variables.
  // `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`.
  // If the proxy server uses HTTPS, then you must set the protocol to `https`. 
  proxy: {
    protocol: 'https',
    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) {
  }),

  decompress: true // default

}

axios 默认配置（简化代码）

  const btns = document.querySelectorAll("button");
    //默认配置
    axios.defaults.method = "POST";
    axios.defaults.baseURL = "https://xxx"
    axios.defaults.withCredentials = true;
    axios.defaults.timeout = 3000;
    btns[1].onclick = function() {

        axios({
            url:"/list",
         
            data:{
                Id:"2"
            }
        }).then(res =>  {
            console.log(res);
        })

    }

axios 实例对象(和axios一样，目的可以向不同服务器发送请求，配置不同的配置)

const instance =  axios.create({
    baseURL:"https://aaa.com",
    timeout: 1000,
    method:"POST"
})
const instance2 =  axios.create({
    baseURL:"https://bbb.com",
    timeout: 3000,
    method:"GET"
})
console.log(instance);
instance({
    url:"/list",
    data:{
        Id:"2"
    }
}).then(res => {
    
})

instance2({
    url:"/list",
    data:{
        Id:"2"
    }
}).then(res => {
    
})

axios 拦截器 interceptors（核心：请求拦截器后进先执行，响应拦截器先进先执行）

// 设置请求拦截器
axios.interceptors.request.use(function (config) {
    //修改请求的参数配置
    return config;
  }, function (error) {
    return Promise.reject(error);
  });

axios.interceptors.response.use(function (response) {
    //处理响应业务
    return response;
  }, function (error) {
    return Promise.reject(error);
  });

axios 取消请求

const btns = document.querySelectorAll("button");
    let cancelCallBack = null;

    btns[1].onclick = function() {
        //实例对象没有 构造函数静态方法和属性
        const instance =  axios.create({
            baseURL:"https://xxx.com",
            timeout: 3000,
            method:"POST"
        })
        instance({
            url:"/list",
            data:{
                Id:"2"
            },
            cancelToken: new axios.CancelToken((c)=>{
                cancelCallBack = c;
            })
        }).then(res => {
            
        })
    }

    btns[2].onclick = function() {
        cancelCallBack();
    }

阅读axios源码学习到什么?

axios对象创建：该对象既可以当对象使用，也可以当函数使用; 任何的发送请求都是有 request方式执行

 //Axios 构造函数
    function Axios(config) {
        this.defaults = config;
        this.interceptors = {
            request: {},
            response: {}
        }
    }
    Axios.prototype.request = function(config) {
        console.log("发送ajax请求", config.method)
    }
    Axios.prototype.get = function(config) {
        return this.request(config);
    }
    Axios.prototype.post = function(config) {
        return this.request(config);
    }

    // 核心方法 生成axios对象： 当对象使用，也可以当方法使用
    function createInstance(config) {
        //实例化一个对象
        let context = new Axios(config);// context.get（） context.post(), 但是不能当作函数使用 context() X
        //创建请求函数
        let instance = Axios.prototype.request.bind(context);// 等价 context.request(), 但是不能当作对象使用 属性和方法
        // 把Axios.prototype对象的方法添加到instance 函数对象中，但是没有构造函数中的属性 default interceptors
        Object.keys(Axios.prototype).forEach(key => {
            instance[key] = Axios.prototype[key].bind(context);
        })
        //给instance 添加 default interceptors
        Object.keys(context).forEach(key => {
            console.log(key)
            instance[key] = context[key];
        })
        return instance;
    }

    let axios = createInstance({method:"post"})
    axios({method:"post"}) //
    axios.request({method:"post"})

axios发送请求过程

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    //Axios 构造函数
    function Axios(config) {
        this.defaults = config;
        this.interceptors = {
            request: {},
            response: {}
        }
    }
    Axios.prototype.request = function(config) {
        //发送请求
        //1 创建promise对象,成功回调
        let promise = Promise.resolve(config);
        //2. 声明数组
        let chains = [dispatchRequest, undefined];//undefined 占位
        //调用 promise对象
        let result =  promise.then(chains[0], chains[1]);
        // 返回 promise对象
        return result;

    }
    
    // 1. 创建实例对象
    function createInstance(config) {
        //实例化一个对象
        let context = new Axios(config);// context.get（） context.post(), 但是不能当作函数使用 context() X
        //创建请求函数
        let instance = Axios.prototype.request.bind(context);// 等价 context.request(), 但是不能当作对象使用 属性和方法
        // 把Axios.prototype对象的方法添加到instance 函数对象中，但是没有构造函数中的属性 default interceptors
        Object.keys(Axios.prototype).forEach(key => {
            instance[key] = Axios.prototype[key].bind(context);
        })
        //给instance 添加 default interceptors
        Object.keys(context).forEach(key => {
            console.log(key)
            instance[key] = context[key];
        })
        return instance;
    }

    //2. dispatchRequest 函数； 处理分发 请求
    function dispatchRequest(config) {
        //调用适配器发送请求
        return xhrAdapter(config).then(response => {
            //对响应的结果处理,暂时不用处理
            // ...
            return response
        }, error => {
            throw error; 
        })
    }

    //3. adaper适配器； xhr发送请求
    function xhrAdapter(config) {
        return new Promise((resolve,reject) => {
            //发送ajax请求  4步
            let xhr = new XMLHttpRequest();
            xhr.open(config.method, config.url);
            xhr.setRequestHeader("Content-Type","application/json");
            xhr.onreadystatechange = function() {
                if(xhr.readyState === 4) {
                    if(xhr.status >= 200 && xhr.status < 300) {
                        //对响应数据 一次格式返回
                        resolve({
                            config:config,
                            data: xhr.response,
                            headers:xhr.getAllResponseHeaders(),
                            request:xhr,
                            status: xhr.status,
                            statusText: xhr.statusText
                        });
                    }else {
                        reject(new Error("请求失败"))
                    }

                }
            }
            //发送json
            xhr.send(JSON.stringify(config.data));
        })
    }


    // 测试
    let axios = Axios.prototype.request.bind(null);
    axios({
            method:"POST",
            url:"https:/xxx/list",
         
            data:{
                Id:"2"
            }
        }).then(res =>  {
            console.log(res);
        })







</script>
</html>

实现拦截器功能原理

通过这次手写拦截器功能，深入了解到，咋样给自己定义的对象添加自定义的遍历方法foreach,promise灵活运用，控制回调函数的执行顺序

axios原理图

axios拦截器实现原理.png
模拟拦截器实现


    //假设这是目标函数： 功能是发送请求的，因为异步所以用promise
    function dispachRequest(config) {
        return new Promise((resolve, reject) => {
            setTimeout(() => {
                //模拟成功状态和失败状态
                // if (config.status == 200) {
                //     console.log("发送请求成功");
                //     resolve(config);
                // } else {
                //     reject("放送请求失败")
                // }
                resolve(config);
            }, 0);
        })
    }

    //定义一个拦截器管理
    //1. 存入回调函数
    //2. 取出回调函数
    function InterceptorManager() {
        this.handlers = [];//存放不同拦截器的回调函数（成功和失败）
    }
    InterceptorManager.prototype.use = function (onResolved, onRejected) {
        this.handlers.push({
            onResolved,
            onRejected
        })
    }
    //给定义一个forEach方法：目的取出 handlers对应的回调函数
    InterceptorManager.prototype.forEach = function (fn) {
        myForEach(this.handlers, function(item) {
            fn(item);
        })

    }

    //自定义一个遍历方法
    function myForEach(arr, fn) {
        for(var i = 0; i < arr.length; i ++) {
            // this指向， item, 索引， 原数据
            fn.call(null, arr[i], i, arr);
        }
    }


    //定义一个拦截器
    let interceptors = {
        request: new InterceptorManager(),
        response: new InterceptorManager()
    }
   
    //测试添加一些 拦截器回调函数
    function addInterceptors() {
    interceptors.request.use(function (config) {
        console.log("请求拦截器成功 -- 1号")
        return config;
    }, function (error) {
        console.log("请求拦截器失败-- 1号")
        return Promise.reject(error);
    });
    interceptors.request.use(function (config) {
        console.log("请求拦截器成功 -- 2号")
        return config;

    }, function (error) {
        console.log("请求拦截器失败 -- 2号")
        return Promise.reject(error);
    });

    //响应拦截器
    interceptors.response.use(function (response) {
        console.log("响应拦截器成功 -- 1号")
        return response;
    }, function (error) {
        console.log("响应拦截器失败-- 1号")

        return Promise.reject(error);
    });
    interceptors.response.use(function (response) {
        console.log("响应拦截器成功 -- 2号")
        return response;
    }, function (error) {
        console.log("响应拦截器失败 -- 2号")
        return Promise.reject(error);
    });
    }
  //添加测试拦截器
    addInterceptors();
   
  
    //主运行函数
    function request(config) {
        //1. 创建promise对象: 把配置参数传递给下一个promise
        let promise = Promise.resolve(config);
        //2. 定义一个数组 
        let chains = [dispachRequest, undefined];
        //2.1 将请求拦截器插入到chains前面
        interceptors.request.forEach(function(interceptor) {
            //记住顺序，失败先插入，因为执行先是成功的
            chains.unshift(interceptor.onResolved,interceptor.onRejected);
        })
        //2.2 将响应拦截器压入到chains后面
         interceptors.response.forEach(function(interceptor) {
            chains.push(interceptor.onResolved,interceptor.onRejected);
        })

        console.log(chains)

        while (chains.length) {
            promise = promise.then(chains.shift(),chains.shift())
        }
        //3. 调用promise对象
        // let result = promise.then(chains[0], chains[1]);
        //返回promise
        return promise;
    }

  //模拟请求
    request({ method: "post"}).then(
        res => {
            console.dir("请求完成的数据"+ res)
        },
        err => {
            console.log(err)
        }
    );

关键效果图

567.jpg

1616580117(1).png

将之前的创建axios, 发送请求，拦截器，进行合并

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