Axios ES2017 (#4787)

* Added AxiosHeaders class;

* Fixed README.md href;

* Fixed a potential bug with headers normalization;

* Fixed a potential bug with headers normalization;
Refactored accessor building routine;
Refactored default transforms;
Removed `normalizeHeaderName` helper;

* Added `Content-Length` accessor;
Added missed `has` accessor to TS types;

* Added `AxiosTransformStream` class;
Added progress capturing ability for node.js environment;
Added `maxRate` option to limit the data rate in node.js environment;
Refactored event handled by `onUploadProgress` && `onDownloadProgress` listeners in browser environment;
Added progress & data rate tests for the http adapter;
Added response stream aborting test;
Added a manual progress capture test for the browser;
Updated TS types;
Added TS tests;
Refactored request abort logic for the http adapter;
Added ability to abort the response stream;

* Remove `stream/promises` & `timers/promises` modules usage in tests;

* Use `abortcontroller-polyfill`;

* Fixed AxiosTransformStream dead-lock in legacy node versions;
Fixed CancelError emitting in streams;

* Reworked AxiosTransformStream internal logic to optimize memory consumption;
Added throwing an error if the request stream was silently destroying (without error) Refers to #3966;

* Treat the destruction of the request stream as a cancellation of the request;
Fixed tests;

* Emit `progress` event in the next tick;

* Initial refactoring;

* Refactored Mocha tests to use ESM;

* Refactored Karma tests to use rollup preprocessor & ESM;
Replaced grunt with gulp;
Improved dev scripts;
Added Babel for rollup build;

* Added default commonjs package export for Node build;
Added automatic contributors list generator for package.json;

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/adapters/http.js

@@ -1,27 +1,33 @@
 'use strict';
 
-var utils = require('./../utils');
-var settle = require('./../core/settle');
-var buildFullPath = require('../core/buildFullPath');
-var buildURL = require('./../helpers/buildURL');
-var getProxyForUrl = require('proxy-from-env').getProxyForUrl;
-var http = require('http');
-var https = require('https');
-var httpFollow = require('follow-redirects/http');
-var httpsFollow = require('follow-redirects/https');
-var url = require('url');
-var zlib = require('zlib');
-var VERSION = require('./../env/data').version;
-var transitionalDefaults = require('../defaults/transitional');
-var AxiosError = require('../core/AxiosError');
-var CanceledError = require('../cancel/CanceledError');
-var platform = require('../platform');
-var fromDataURI = require('../helpers/fromDataURI');
-var stream = require('stream');
+import utils from './../utils.js';
+import settle from './../core/settle.js';
+import buildFullPath from '../core/buildFullPath.js';
+import buildURL from './../helpers/buildURL.js';
+import {getProxyForUrl} from 'proxy-from-env';
+import http from 'http';
+import https from 'https';
+import followRedirects from 'follow-redirects';
+import url from 'url';
+import zlib from 'zlib';
+import {VERSION} from '../env/data.js';
+import transitionalDefaults from '../defaults/transitional.js';
+import AxiosError from '../core/AxiosError.js';
+import CanceledError from '../cancel/CanceledError.js';
+import platform from '../platform/index.js';
+import fromDataURI from '../helpers/fromDataURI.js';
+import stream from 'stream';
+import AxiosHeaders from '../core/AxiosHeaders.js';
+import AxiosTransformStream from '../helpers/AxiosTransformStream.js';
+import EventEmitter from 'events';
 
-var isHttps = /https:?/;
+const isBrotliSupported = utils.isFunction(zlib.createBrotliDecompress);
 
-var supportedProtocols = platform.protocols.map(function(protocol) {
+const {http: httpFollow, https: httpsFollow} = followRedirects;
+
+const isHttps = /https:?/;
+
+const supportedProtocols = platform.protocols.map(protocol => {
   return protocol + ':';
 });
 
@@ -52,9 +58,9 @@ function dispatchBeforeRedirect(options) {
  * @returns {http.ClientRequestArgs}
  */
 function setProxy(options, configProxy, location) {
-  var proxy = configProxy;
+  let proxy = configProxy;
   if (!proxy && proxy !== false) {
-    var proxyUrl = getProxyForUrl(location);
+    const proxyUrl = getProxyForUrl(location);
     if (proxyUrl) {
       proxy = url.parse(proxyUrl);
       // replace 'host' since the proxy object is not a URL object
@@ -68,7 +74,7 @@ function setProxy(options, configProxy, location) {
       if (proxy.auth.username || proxy.auth.password) {
         proxy.auth = (proxy.auth.username || '') + ':' + (proxy.auth.password || '');
       }
-      var base64 = Buffer
+      const base64 = Buffer
         .from(proxy.auth, 'utf8')
         .toString('base64');
       options.headers['Proxy-Authorization'] = 'Basic ' + base64;
@@ -92,10 +98,25 @@ function setProxy(options, configProxy, location) {
 }
 
 /*eslint consistent-return:0*/
-module.exports = function httpAdapter(config) {
+export default function httpAdapter(config) {
   return new Promise(function dispatchHttpRequest(resolvePromise, rejectPromise) {
-    var onCanceled;
-    function done() {
+    let onCanceled;
+    let data = config.data;
+    const responseType = config.responseType;
+    const responseEncoding = config.responseEncoding;
+    const method = config.method.toUpperCase();
+    let isFinished;
+    let isDone;
+    let rejected = false;
+    let req;
+
+    // temporary internal emitter until the AxiosRequest class will be implemented
+    const emitter = new EventEmitter();
+
+    function onFinished() {
+      if (isFinished) return;
+      isFinished = true;
+
       if (config.cancelToken) {
         config.cancelToken.unsubscribe(onCanceled);
       }
@@ -103,36 +124,58 @@ module.exports = function httpAdapter(config) {
       if (config.signal) {
         config.signal.removeEventListener('abort', onCanceled);
       }
+
+      emitter.removeAllListeners();
     }
-    var resolve = function resolve(value) {
-      done();
-      resolvePromise(value);
+
+    function done(value, isRejected) {
+      if (isDone) return;
+
+      isDone = true;
+
+      if (isRejected) {
+        rejected = true;
+        onFinished();
+      }
+
+      isRejected ? rejectPromise(value) : resolvePromise(value);
+    }
+
+    const resolve = function resolve(value) {
+      done(value);
     };
-    var rejected = false;
-    var reject = function reject(value) {
-      done();
-      rejected = true;
-      rejectPromise(value);
+
+    const reject = function reject(value) {
+      done(value, true);
     };
-    var data = config.data;
-    var responseType = config.responseType;
-    var responseEncoding = config.responseEncoding;
-    var method = config.method.toUpperCase();
+
+    function abort(reason) {
+      emitter.emit('abort', !reason || reason.type ? new CanceledError(null, config, req) : reason);
+    }
+
+    emitter.once('abort', reject);
+
+    if (config.cancelToken || config.signal) {
+      config.cancelToken && config.cancelToken.subscribe(abort);
+      if (config.signal) {
+        config.signal.aborted ? abort() : config.signal.addEventListener('abort', abort);
+      }
+    }
 
     // Parse url
-    var fullPath = buildFullPath(config.baseURL, config.url);
-    var parsed = url.parse(fullPath);
-    var protocol = parsed.protocol || supportedProtocols[0];
+    const fullPath = buildFullPath(config.baseURL, config.url);
+    const parsed = url.parse(fullPath);
+    const protocol = parsed.protocol || supportedProtocols[0];
 
     if (protocol === 'data:') {
-      var convertedData;
+      let convertedData;
 
       if (method !== 'GET') {
         return settle(resolve, reject, {
           status: 405,
           statusText: 'method not allowed',
           headers: {},
-          config: config
+          config
         });
       }
 
@@ -159,7 +202,7 @@ module.exports = function httpAdapter(config) {
         status: 200,
         statusText: 'OK',
         headers: {},
-        config: config
+        config
       });
     }
 
@@ -171,29 +214,23 @@ module.exports = function httpAdapter(config) {
       ));
     }
 
-    var headers = config.headers;
-    var headerNames = {};
-
-    Object.keys(headers).forEach(function storeLowerName(name) {
-      headerNames[name.toLowerCase()] = name;
-    });
+    const headers = AxiosHeaders.from(config.headers).normalize();
 
     // Set User-Agent (required by some servers)
     // See https://github.com/axios/axios/issues/69
-    if ('user-agent' in headerNames) {
-      // User-Agent is specified; handle case where no UA header is desired
-      if (!headers[headerNames['user-agent']]) {
-        delete headers[headerNames['user-agent']];
-      }
-      // Otherwise, use specified value
-    } else {
-      // Only set header if it hasn't been set in config
-      headers['User-Agent'] = 'axios/' + VERSION;
-    }
+    // User-Agent is specified; handle case where no UA header is desired
+    // Only set header if it hasn't been set in config
+    headers.set('User-Agent', 'axios/' + VERSION, false);
+
+    const onDownloadProgress = config.onDownloadProgress;
+    const onUploadProgress = config.onUploadProgress;
+    const maxRate = config.maxRate;
+    let maxUploadRate = undefined;
+    let maxDownloadRate = undefined;
 
     // support for https://www.npmjs.com/package/form-data api
     if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) {
-      Object.assign(headers, data.getHeaders());
+      headers.set(data.getHeaders());
     } else if (data && !utils.isStream(data)) {
       if (Buffer.isBuffer(data)) {
         // Nothing to do...
@@ -209,6 +246,9 @@ module.exports = function httpAdapter(config) {
         ));
       }
 
+      // Add Content-Length header if data exists
+      headers.set('Content-Length', data.length, false);
+
       if (config.maxBodyLength > -1 && data.length > config.maxBodyLength) {
         return reject(new AxiosError(
           'Request body larger than maxBodyLength limit',
@@ -216,49 +256,70 @@ module.exports = function httpAdapter(config) {
           config
         ));
       }
+    }
 
-      // Add Content-Length header if data exists
-      if (!headerNames['content-length']) {
-        headers['Content-Length'] = data.length;
+    const contentLength = +headers.getContentLength();
+
+    if (utils.isArray(maxRate)) {
+      maxUploadRate = maxRate[0];
+      maxDownloadRate = maxRate[1];
+    } else {
+      maxUploadRate = maxDownloadRate = maxRate;
+    }
+
+    if (data && (onUploadProgress || maxUploadRate)) {
+      if (!utils.isStream(data)) {
+        data = stream.Readable.from(data, {objectMode: false});
       }
+
+      data = stream.pipeline([data, new AxiosTransformStream({
+        length: utils.toFiniteNumber(contentLength),
+        maxRate: utils.toFiniteNumber(maxUploadRate)
+      })], utils.noop);
+
+      onUploadProgress && data.on('progress', progress => {
+        onUploadProgress(Object.assign(progress, {
+          upload: true
+        }));
+      });
     }
 
     // HTTP basic authentication
-    var auth = undefined;
+    let auth = undefined;
     if (config.auth) {
-      var username = config.auth.username || '';
-      var password = config.auth.password || '';
+      const username = config.auth.username || '';
+      const password = config.auth.password || '';
       auth = username + ':' + password;
     }
 
     if (!auth && parsed.auth) {
-      var urlAuth = parsed.auth.split(':');
-      var urlUsername = urlAuth[0] || '';
-      var urlPassword = urlAuth[1] || '';
+      const urlAuth = parsed.auth.split(':');
+      const urlUsername = urlAuth[0] || '';
+      const urlPassword = urlAuth[1] || '';
       auth = urlUsername + ':' + urlPassword;
     }
 
-    if (auth && headerNames.authorization) {
-      delete headers[headerNames.authorization];
-    }
+    auth && headers.delete('authorization');
 
     try {
       buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, '');
     } catch (err) {
-      var customErr = new Error(err.message);
+      const customErr = new Error(err.message);
       customErr.config = config;
       customErr.url = config.url;
       customErr.exists = true;
-      reject(customErr);
+      return reject(customErr);
     }
 
-    var options = {
+    headers.set('Accept-Encoding', 'gzip, deflate, gzip, br', false);
+
+    const options = {
       path: buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, ''),
-      method: method,
-      headers: headers,
+      method,
+      headers: headers.toJSON(),
       agents: { http: config.httpAgent, https: config.httpsAgent },
-      auth: auth,
-      protocol: protocol,
+      auth,
+      protocol,
       beforeRedirect: dispatchBeforeRedirect,
       beforeRedirects: {}
     };
@@ -271,8 +332,8 @@ module.exports = function httpAdapter(config) {
       setProxy(options, config.proxy, protocol + '//' + parsed.hostname + (parsed.port ? ':' + parsed.port : '') + options.path);
     }
 
-    var transport;
-    var isHttpsRequest = isHttps.test(options.protocol);
+    let transport;
+    const isHttpsRequest = isHttps.test(options.protocol);
     options.agent = isHttpsRequest ? config.httpsAgent : config.httpAgent;
     if (config.transport) {
       transport = config.transport;
@@ -300,14 +361,16 @@ module.exports = function httpAdapter(config) {
     }
 
     // Create the request
-    var req = transport.request(options, function handleResponse(res) {
-      if (req.aborted) return;
+    req = transport.request(options, function handleResponse(res) {
+      if (req.destroyed) return;
+
+      const streams = [res];
 
       // uncompress the response body transparently if required
-      var responseStream = res;
+      let responseStream = res;
 
       // return the last request in case of redirects
-      var lastRequest = res.req || req;
+      const lastRequest = res.req || req;
 
       // if decompress disabled we should not decompress
       if (config.decompress !== false) {
@@ -323,19 +386,48 @@ module.exports = function httpAdapter(config) {
         case 'compress':
         case 'deflate':
           // add the unzipper to the body stream processing pipeline
-          responseStream = responseStream.pipe(zlib.createUnzip());
+          streams.push(zlib.createUnzip());
 
           // remove the content-encoding in order to not confuse downstream operations
           delete res.headers['content-encoding'];
           break;
+        case 'br':
+          if (isBrotliSupported) {
+            streams.push(zlib.createBrotliDecompress());
+            delete res.headers['content-encoding'];
+          }
         }
       }
 
-      var response = {
+      if (onDownloadProgress) {
+        const responseLength = +res.headers['content-length'];
+
+        const transformStream = new AxiosTransformStream({
+          length: utils.toFiniteNumber(responseLength),
+          maxRate: utils.toFiniteNumber(maxDownloadRate)
+        });
+
+        onDownloadProgress && transformStream.on('progress', progress => {
+          onDownloadProgress(Object.assign(progress, {
+            download: true
+          }));
+        });
+
+        streams.push(transformStream);
+      }
+
+      responseStream = streams.length > 1 ? stream.pipeline(streams, utils.noop) : streams[0];
+
+      const offListeners = stream.finished(responseStream, () => {
+        offListeners();
+        onFinished();
+      });
+
+      const response = {
         status: res.statusCode,
         statusText: res.statusMessage,
-        headers: res.headers,
-        config: config,
+        headers: new AxiosHeaders(res.headers),
+        config,
         request: lastRequest
       };
 
@@ -343,8 +435,9 @@ module.exports = function httpAdapter(config) {
         response.data = responseStream;
         settle(resolve, reject, response);
       } else {
-        var responseBuffer = [];
-        var totalResponseBytes = 0;
+        const responseBuffer = [];
+        let totalResponseBytes = 0;
+
         responseStream.on('data', function handleStreamData(chunk) {
           responseBuffer.push(chunk);
           totalResponseBytes += chunk.length;
@@ -363,23 +456,25 @@ module.exports = function httpAdapter(config) {
           if (rejected) {
             return;
           }
-          responseStream.destroy();
-          reject(new AxiosError(
+
+          const err = new AxiosError(
             'maxContentLength size of ' + config.maxContentLength + ' exceeded',
             AxiosError.ERR_BAD_RESPONSE,
             config,
             lastRequest
-          ));
+          );
+          responseStream.destroy(err);
+          reject(err);
         });
 
         responseStream.on('error', function handleStreamError(err) {
-          if (req.aborted) return;
+          if (req.destroyed) return;
           reject(AxiosError.from(err, null, config, lastRequest));
         });
 
         responseStream.on('end', function handleStreamEnd() {
           try {
-            var responseData = responseBuffer.length === 1 ? responseBuffer[0] : Buffer.concat(responseBuffer);
+            let responseData = responseBuffer.length === 1 ? responseBuffer[0] : Buffer.concat(responseBuffer);
             if (responseType !== 'arraybuffer') {
               responseData = responseData.toString(responseEncoding);
               if (!responseEncoding || responseEncoding === 'utf8') {
@@ -393,6 +488,18 @@ module.exports = function httpAdapter(config) {
           settle(resolve, reject, response);
         });
       }
+
+      emitter.once('abort', err => {
+        if (!responseStream.destroyed) {
+          responseStream.emit('error', err);
+          responseStream.destroy();
+        }
+      });
+    });
+
+    emitter.once('abort', err => {
+      reject(err);
+      req.destroy(err);
     });
 
     // Handle errors
@@ -411,7 +518,7 @@ module.exports = function httpAdapter(config) {
     // Handle request timeout
     if (config.timeout) {
       // This is forcing a int timeout to avoid problems if the `req` interface doesn't handle other types.
-      var timeout = parseInt(config.timeout, 10);
+      const timeout = parseInt(config.timeout, 10);
 
       if (isNaN(timeout)) {
         reject(new AxiosError(
@@ -430,9 +537,9 @@ module.exports = function httpAdapter(config) {
       // And then these socket which be hang up will devouring CPU little by little.
       // ClientRequest.setTimeout will be fired on the specify milliseconds, and can make sure that abort() will be fired after connect.
       req.setTimeout(timeout, function handleRequestTimeout() {
-        req.abort();
-        var timeoutErrorMessage = config.timeout ? 'timeout of ' + config.timeout + 'ms exceeded' : 'timeout exceeded';
-        var transitional = config.transitional || transitionalDefaults;
+        if (isDone) return;
+        let timeoutErrorMessage = config.timeout ? 'timeout of ' + config.timeout + 'ms exceeded' : 'timeout exceeded';
+        const transitional = config.transitional || transitionalDefaults;
         if (config.timeoutErrorMessage) {
           timeoutErrorMessage = config.timeoutErrorMessage;
         }
@@ -442,33 +549,34 @@ module.exports = function httpAdapter(config) {
           config,
           req
         ));
+        abort();
       });
     }
 
-    if (config.cancelToken || config.signal) {
-      // Handle cancellation
-      // eslint-disable-next-line func-names
-      onCanceled = function(cancel) {
-        if (req.aborted) return;
-
-        req.abort();
-        reject(!cancel || cancel.type ? new CanceledError(null, config, req) : cancel);
-      };
-
-      config.cancelToken && config.cancelToken.subscribe(onCanceled);
-      if (config.signal) {
-        config.signal.aborted ? onCanceled() : config.signal.addEventListener('abort', onCanceled);
-      }
-    }
-
 
     // Send the request
     if (utils.isStream(data)) {
-      data.on('error', function handleStreamError(err) {
-        reject(AxiosError.from(err, config, null, req));
-      }).pipe(req);
+      let ended = false;
+      let errored = false;
+
+      data.on('end', () => {
+        ended = true;
+      });
+
+      data.once('error', err => {
+        errored = true;
+        req.destroy(err);
+      });
+
+      data.on('close', () => {
+        if (!ended && !errored) {
+          abort(new CanceledError('Request stream has been aborted', config, req));
+        }
+      });
+
+      data.pipe(req);
     } else {
       req.end(data);
     }
   });
-};
+}

lib/adapters/index.js

@@ -0,0 +1,33 @@
+import utils from '../utils.js';
+import httpAdapter from './http.js';
+import xhrAdapter from './xhr.js';
+
+const adapters = {
+  http: httpAdapter,
+  xhr: xhrAdapter
+}
+
+export default {
+  getAdapter: (nameOrAdapter) => {
+    if(utils.isString(nameOrAdapter)){
+      const adapter = adapters[nameOrAdapter];
+
+      if (!nameOrAdapter) {
+        throw Error(
+          utils.hasOwnProp(nameOrAdapter) ?
+            `Adapter '${nameOrAdapter}' is not available in the build` :
+            `Can not resolve adapter '${nameOrAdapter}'`
+        );
+      }
+
+      return adapter
+    }
+
+    if (!utils.isFunction(nameOrAdapter)) {
+      throw new TypeError('adapter is not a function');
+    }
+
+    return nameOrAdapter;
+  },
+  adapters
+}

lib/adapters/xhr.js

@@ -1,24 +1,53 @@
 'use strict';
 
-var utils = require('./../utils');
-var settle = require('./../core/settle');
-var cookies = require('./../helpers/cookies');
-var buildURL = require('./../helpers/buildURL');
-var buildFullPath = require('../core/buildFullPath');
-var parseHeaders = require('./../helpers/parseHeaders');
-var isURLSameOrigin = require('./../helpers/isURLSameOrigin');
-var transitionalDefaults = require('../defaults/transitional');
-var AxiosError = require('../core/AxiosError');
-var CanceledError = require('../cancel/CanceledError');
-var parseProtocol = require('../helpers/parseProtocol');
-var platform = require('../platform');
+import utils from './../utils.js';
+import settle from './../core/settle.js';
+import cookies from './../helpers/cookies.js';
+import buildURL from './../helpers/buildURL.js';
+import buildFullPath from '../core/buildFullPath.js';
+import isURLSameOrigin from './../helpers/isURLSameOrigin.js';
+import transitionalDefaults from '../defaults/transitional.js';
+import AxiosError from '../core/AxiosError.js';
+import CanceledError from '../cancel/CanceledError.js';
+import parseProtocol from '../helpers/parseProtocol.js';
+import platform from '../platform/index.js';
+import AxiosHeaders from '../core/AxiosHeaders.js';
+import speedometer from '../helpers/speedometer.js';
 
-module.exports = function xhrAdapter(config) {
+function progressEventReducer(listener, isDownloadStream) {
+  let bytesNotified = 0;
+  const _speedometer = speedometer(50, 250);
+
+  return e => {
+    const loaded = e.loaded;
+    const total = e.lengthComputable ? e.total : undefined;
+    const progressBytes = loaded - bytesNotified;
+    const rate = _speedometer(progressBytes);
+    const inRange = loaded <= total;
+
+    bytesNotified = loaded;
+
+    const data = {
+      loaded,
+      total,
+      progress: total ? (loaded / total) : undefined,
+      bytes: progressBytes,
+      rate: rate ? rate : undefined,
+      estimated: rate && total && inRange ? (total - loaded) / rate : undefined
+    };
+
+    data[isDownloadStream ? 'download' : 'upload'] = true;
+
+    listener(data);
+  };
+}
+
+export default function xhrAdapter(config) {
   return new Promise(function dispatchXhrRequest(resolve, reject) {
-    var requestData = config.data;
-    var requestHeaders = config.headers;
-    var responseType = config.responseType;
-    var onCanceled;
+    let requestData = config.data;
+    const requestHeaders = AxiosHeaders.from(config.headers).normalize();
+    const responseType = config.responseType;
+    let onCanceled;
     function done() {
       if (config.cancelToken) {
         config.cancelToken.unsubscribe(onCanceled);
@@ -30,19 +59,19 @@ module.exports = function xhrAdapter(config) {
     }
 
     if (utils.isFormData(requestData) && utils.isStandardBrowserEnv()) {
-      delete requestHeaders['Content-Type']; // Let the browser set it
+      requestHeaders.setContentType(false); // Let the browser set it
     }
 
-    var request = new XMLHttpRequest();
+    let request = new XMLHttpRequest();
 
     // HTTP basic authentication
     if (config.auth) {
-      var username = config.auth.username || '';
-      var password = config.auth.password ? unescape(encodeURIComponent(config.auth.password)) : '';
-      requestHeaders.Authorization = 'Basic ' + btoa(username + ':' + password);
+      const username = config.auth.username || '';
+      const password = config.auth.password ? unescape(encodeURIComponent(config.auth.password)) : '';
+      requestHeaders.set('Authorization', 'Basic ' + btoa(username + ':' + password));
     }
 
-    var fullPath = buildFullPath(config.baseURL, config.url);
+    const fullPath = buildFullPath(config.baseURL, config.url);
 
     request.open(config.method.toUpperCase(), buildURL(fullPath, config.params, config.paramsSerializer), true);
 
@@ -54,16 +83,18 @@ module.exports = function xhrAdapter(config) {
         return;
       }
       // Prepare the response
-      var responseHeaders = 'getAllResponseHeaders' in request ? parseHeaders(request.getAllResponseHeaders()) : null;
-      var responseData = !responseType || responseType === 'text' ||  responseType === 'json' ?
+      const responseHeaders = AxiosHeaders.from(
+        'getAllResponseHeaders' in request && request.getAllResponseHeaders()
+      );
+      const responseData = !responseType || responseType === 'text' ||  responseType === 'json' ?
         request.responseText : request.response;
-      var response = {
+      const response = {
         data: responseData,
         status: request.status,
         statusText: request.statusText,
         headers: responseHeaders,
-        config: config,
-        request: request
+        config,
+        request
       };
 
       settle(function _resolve(value) {
@@ -125,8 +156,8 @@ module.exports = function xhrAdapter(config) {
 
     // Handle timeout
     request.ontimeout = function handleTimeout() {
-      var timeoutErrorMessage = config.timeout ? 'timeout of ' + config.timeout + 'ms exceeded' : 'timeout exceeded';
-      var transitional = config.transitional || transitionalDefaults;
+      let timeoutErrorMessage = config.timeout ? 'timeout of ' + config.timeout + 'ms exceeded' : 'timeout exceeded';
+      const transitional = config.transitional || transitionalDefaults;
       if (config.timeoutErrorMessage) {
         timeoutErrorMessage = config.timeoutErrorMessage;
       }
@@ -145,25 +176,21 @@ module.exports = function xhrAdapter(config) {
     // Specifically not if we're in a web worker, or react-native.
     if (utils.isStandardBrowserEnv()) {
       // Add xsrf header
-      var xsrfValue = (config.withCredentials || isURLSameOrigin(fullPath)) && config.xsrfCookieName ?
-        cookies.read(config.xsrfCookieName) :
-        undefined;
+      const xsrfValue = (config.withCredentials || isURLSameOrigin(fullPath))
+        && config.xsrfCookieName && cookies.read(config.xsrfCookieName);
 
       if (xsrfValue) {
-        requestHeaders[config.xsrfHeaderName] = xsrfValue;
+        requestHeaders.set(config.xsrfHeaderName, xsrfValue);
       }
     }
 
+    // Remove Content-Type if data is undefined
+    requestData === undefined && requestHeaders.setContentType(null);
+
     // Add headers to the request
     if ('setRequestHeader' in request) {
-      utils.forEach(requestHeaders, function setRequestHeader(val, key) {
-        if (typeof requestData === 'undefined' && key.toLowerCase() === 'content-type') {
-          // Remove Content-Type if data is undefined
-          delete requestHeaders[key];
-        } else {
-          // Otherwise add header to the request
-          request.setRequestHeader(key, val);
-        }
+      utils.forEach(requestHeaders.toJSON(), function setRequestHeader(val, key) {
+        request.setRequestHeader(key, val);
       });
     }
 
@@ -179,22 +206,22 @@ module.exports = function xhrAdapter(config) {
 
     // Handle progress if needed
     if (typeof config.onDownloadProgress === 'function') {
-      request.addEventListener('progress', config.onDownloadProgress);
+      request.addEventListener('progress', progressEventReducer(config.onDownloadProgress, true));
     }
 
     // Not all browsers support upload events
     if (typeof config.onUploadProgress === 'function' && request.upload) {
-      request.upload.addEventListener('progress', config.onUploadProgress);
+      request.upload.addEventListener('progress', progressEventReducer(config.onUploadProgress));
     }
 
     if (config.cancelToken || config.signal) {
       // Handle cancellation
       // eslint-disable-next-line func-names
-      onCanceled = function(cancel) {
+      onCanceled = cancel => {
         if (!request) {
           return;
         }
-        reject(!cancel || cancel.type ? new CanceledError(null, config, req) : cancel);
+        reject(!cancel || cancel.type ? new CanceledError(null, config, request) : cancel);
         request.abort();
         request = null;
       };
@@ -210,7 +237,7 @@ module.exports = function xhrAdapter(config) {
       requestData = null;
     }
 
-    var protocol = parseProtocol(fullPath);
+    const protocol = parseProtocol(fullPath);
 
     if (protocol && platform.protocols.indexOf(protocol) === -1) {
       reject(new AxiosError('Unsupported protocol ' + protocol + ':', AxiosError.ERR_BAD_REQUEST, config));
@@ -221,4 +248,4 @@ module.exports = function xhrAdapter(config) {
     // Send the request
     request.send(requestData);
   });
-};
+}