一比一还原axios源码（二）—— 请求响应处理

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

function transformRequest(data) {
  if (utils.isPlainObject(data)) {
    return JSON.stringify(data);
  }
  return data;
}

function isPlainObject(val) {
  if (toString.call(val) !== "[object Object]") {
    return false;
  }

  var prototype = Object.getPrototypeOf(val);
  return prototype === null || prototype === Object.prototype;
}

function processHeaders(headers, data) {
  normalizeHeaderName(headers, "Content-Type");
  if (utils.isPlainObject(data)) {
    if (headers && !headers["Content-Type"]) {
      headers["Content-Type"] = "application/json;charset=utf-8";
    }
  }
  return headers;
}

    config.headers = processHeaders(config.headers || {}, config.data);

Object.keys(config.headers).forEach((name) => {
      if (config.data === null && name.toLowerCase() === "content-type") {
        delete config.headers[name];
      } else {
        request.setRequestHeader(name, config.headers[name]);
      }
    });

request.onreadystatechange = function handleLoad() {
      if (request.readyState !== 4) {
        return;
      }

      const responseHeaders = parseHeaders(request.getAllResponseHeaders());
      const responseData =
        config.responseType && config.responseType !== "text"
          ? request.response
          : request.responseText;
      const response = {
        data: responseData,
        status: request.status,
        statusText: request.statusText,
        headers: responseHeaders,
        config,
        request,
      };
      resolve(response);
    };

"use strict";

import utils from "../utils";

// Headers whose duplicates are ignored by node
// c.f. https://nodejs.org/api/http.html#http_message_headers
// 这是我们需要忽略的header
var ignoreDuplicateOf = [
  "age",
  "authorization",
  "content-length",
  "content-type",
  "etag",
  "expires",
  "from",
  "host",
  "if-modified-since",
  "if-unmodified-since",
  "last-modified",
  "location",
  "max-forwards",
  "proxy-authorization",
  "referer",
  "retry-after",
  "user-agent",
];

/**
 * Parse headers into an object
 *
 * ```
 * Date: Wed, 27 Aug 2014 08:58:49 GMT
 * Content-Type: application/json
 * Connection: keep-alive
 * Transfer-Encoding: chunked
 * ```
 *
 * @param {String} headers Headers needing to be parsed
 * @returns {Object} Headers parsed into an object
 */
export default function parseHeaders(headers) {
  var parsed = {};
  var key;
  var val;
  var i;
  // 没有headers就返回个空对象
  if (!headers) {
    return parsed;
  }
  // 用自定义的forEach方法来遍历分割后的headers
  utils.forEach(headers.split("\n"), function parser(line) {
    // 这时候，line还是个字符串，i就是每一个key、value中间的位置
    i = line.indexOf(":");
    // 分割key，去空格
    key = utils.trim(line.substr(0, i)).toLowerCase();
    // 分割value，去空格
    val = utils.trim(line.substr(i + 1));

    if (key) {
      // 如果存在key并且是重复项，则略过
      if (parsed[key] && ignoreDuplicateOf.indexOf(key) >= 0) {
        return;
      }
      // 如果key是set-cookie，那么用数组合并作为值
      if (key === "set-cookie") {
        parsed[key] = (parsed[key] ? parsed[key] : []).concat([val]);
      } else {
        // 否则用逗号分隔已有的值或者直接设置值
        parsed[key] = parsed[key] ? parsed[key] + ", " + val : val;
      }
    }
  });

  return parsed;
}

      const responseData =
        config.responseType && config.responseType !== "text"
          ? request.response
          : request.responseText;

const response = {
        data: responseData,
        status: request.status,
        statusText: request.statusText,
        headers: responseHeaders,
        config,
        request,
      };
      resolve(response);

axios({
   method:"post",
   url:"xxx",
   params:{},
   data:{},
   responseType:"",
   headers:{},     
}).then((res) => {
   console.log(res) 
})