基于TypeScript从零重构axios

好的，让我们开始重构axios！

首先，我们需要安装TypeScript和相关的依赖。运行以下命令：

npm install typescript @types/node @types/qs @types/form-data

接下来，我们需要创建一个tsconfig.json文件。在项目根目录下创建一个名为tsconfig.json的文件，并将以下内容复制到其中：

{
  "compilerOptions": {
    "lib": ["es6", "dom"],
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "declaration": true,
    "sourceMap": true,
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  },
  "exclude": ["node_modules"]
}

现在，我们可以开始重构axios的代码了。

首先，我们需要将axios的代码转换为TypeScript。我们可以将所有的JavaScript文件重命名为.ts文件，并使用TypeScript的语法更新代码。例如，我们可以使用类型注释来定义函数的参数类型和返回类型。

下面是一个使用TypeScript语法重构的示例：

import * as http from 'http';
import * as https from 'https';
import * as url from 'url';
import * as zlib from 'zlib';
import { Cancel, CancelToken } from './cancel';
import { isFormData } from './utils';
import settle from './core/settle';
import buildURL from './helpers/buildURL';
import parseHeaders from './helpers/parseHeaders';
import createError from './core/createError';
import enhanceError from './core/enhanceError';
import defaults from './defaults';

interface AxiosRequestConfig {
  url?: string;
  method?: string;
  baseURL?: string;
  headers?: any;
  params?: any;
  data?: any;
  timeout?: number;
  withCredentials?: boolean;
  responseType?: XMLHttpRequestResponseType;
  xsrfCookieName?: string;
  xsrfHeaderName?: string;
  onDownloadProgress?: (progressEvent: any) => void;
  onUploadProgress?: (progressEvent: any) => void;
  cancelToken?: CancelToken;
}

interface AxiosResponse<T = any> {
  data: T;
  status: number;
  statusText: string;
  headers: any;
  config: AxiosRequestConfig;
  request?: any;
}

interface AxiosError<T = any> extends Error {
  config: AxiosRequestConfig;
  code?: string;
  request?: any;
  response?: AxiosResponse<T>;
  isAxiosError: boolean;
}

interface AxiosPromise<T = any> extends Promise<AxiosResponse<T>> {}

interface Axios {
  defaults: AxiosRequestConfig;
  interceptors: {
    request: AxiosInterceptorManager<AxiosRequestConfig>;
    response: AxiosInterceptorManager<AxiosResponse>;
  };
  request<T = any>(config: AxiosRequestConfig): AxiosPromise<T>;
  get<T = any>(url: string, config?: AxiosRequestConfig): AxiosPromise<T>;
  delete<T = any>(url: string, config?: AxiosRequestConfig): AxiosPromise<T>;
  head<T = any>(url: string, config?: AxiosRequestConfig): AxiosPromise<T>;
  options<T = any>(url: string, config?: AxiosRequestConfig): AxiosPromise<T>;
  post<T = any>(url: string, data?: any, config?: AxiosRequestConfig): AxiosPromise<T>;
  put<T = any>(url: string, data?: any, config?: AxiosRequestConfig): AxiosPromise<T>;
  patch<T = any>(url: string, data?: any, config?: AxiosRequestConfig): AxiosPromise<T>;
}

interface AxiosInstance extends Axios {
  <T = any>(config: AxiosRequestConfig): AxiosPromise<T>;
  <T = any>(url: string, config?: AxiosRequestConfig): AxiosPromise<T>;
}

interface AxiosStatic extends AxiosInstance {
  create(config?: AxiosRequestConfig): AxiosInstance;
  CancelToken: CancelTokenStatic;
  Cancel: CancelStatic;
  isCancel: (value: any) => boolean;
}

interface AxiosInterceptorManager<T> {
  use(resolved: ResolvedFn<T>, rejected?: RejectedFn): number;
  eject(id: number): void;
}

interface ResolvedFn<T> {
  (val: T): T | Promise<T>;
}

interface RejectedFn {
  (error: any): any;
}

interface CancelToken {
  promise: Promise<Cancel>;
  reason?: Cancel;
  throwIfRequested(): void;
}

interface Canceler {
  (message?: string): void;
}

interface CancelExecutor {
  (cancel: Canceler): void;
}

interface CancelTokenSource {
  token: CancelToken;
  cancel: Canceler;
}

interface CancelTokenStatic {
  new (executor: CancelExecutor): CancelToken;
  source(): CancelTokenSource;
}

interface Cancel {
  message?: string;
}

interface CancelStatic {
  new (message?: string): Cancel;
}

function axios<T = any>(config: AxiosRequestConfig): AxiosPromise<T> {
  return dispatchRequest(config);
}

function createInstance(config: AxiosRequestConfig): AxiosInstance {
  const context = new Axios(config);
  const instance = Axios.prototype.request.bind(context);

  Object.assign(instance, Axios.prototype, context);

  return instance as AxiosInstance;
}

const axiosInstance = createInstance(defaults);
axiosInstance.create = function create(config) {
  return createInstance(Object.assign(defaults, config));
};

function getDefaultAdapter() {
  let adapter;
  if (typeof XMLHttpRequest !== 'undefined') {
    adapter = require('./adapters/xhr');
  } else if (typeof http !== 'undefined') {
    adapter = require('./adapters/http');
  } else if (typeof https !== 'undefined') {
    adapter = require('./adapters/http');
  }
  return adapter;
}

function dispatchRequest<T = any>(config: AxiosRequestConfig): AxiosPromise<T> {
  throwIfCancellationRequested(config.cancelToken);

  processConfig(config);
  return getDefaultAdapter()(config).then((response) => {
    return transformResponseData(response);
  }, (error) => {
    if (error && error.response) {
      error.response = transformResponseData(error.response);
    }
    return Promise.reject(error);
  }).then((response) => {
    settle(resolve, reject, response);
    return response;
  }, (error) => {
    settle(resolve, reject, enhanceError(error));
    return Promise.reject(enhanceError(error));
  });
}

function processConfig(config: AxiosRequestConfig): void {
  config.url = transformURL(config);
  config.headers = transformHeaders(config);
  config.data = transformData(config);
  config.params = transformParams(config);
}

function transformURL(config: AxiosRequestConfig): string {
  const { url, params, baseURL } = config;
  return buildURL(url!, params, baseURL);
}

function transformHeaders(config: AxiosRequestConfig): any {
  const { headers = {}, data } = config;
  return Object.assign(headers.common || {}, headers[config.method!] || {}, headers, data ? data.headers : null);
}

function transformData(config: AxiosRequestConfig): any {
  const { data } = config;
  return isFormData(data) ? data : JSON.stringify(data);
}

function transformParams(config: AxiosRequestConfig): any {
  const { params } = config;
  return params ? params : null;
}

function transformResponseData(response: AxiosResponse): AxiosResponse {
  response.data = transformData(response);
  response.headers = parseHeaders(response.headers, response.config);
  response.data = transformData(response);
  return response;
}

function throwIfCancellationRequested(cancelToken?: CancelToken): void {
  if (cancelToken) {
    cancelToken.throwIfRequested();
  }
}

export default axiosInstance;

现在我们已经将axios的代码转换为了TypeScript，接下来我们需要更新一下项目的结构。

我们可以将所有的TypeScript代码放在一个src目录下，并将编译后的JavaScript代码放在一个dist目录下。这样做可以使我们的代码更加结构化和易于管理。

接下来，我们需要更新package.json文件中的scripts字段，以便使用TypeScript编译我们的代码。在scripts字段中添加以下内容：

"scripts": {
  "build": "tsc"
}

现在我们可以运行npm run build命令来编译我们的代码了。

最后，我们需要更新我们的引用代码，以便使用重构后的axios。例如，我们可以使用以下代码来发送一个GET请求：

import axios from './dist/axios';

axios.get('/user', {
  params: {
    ID: 12345
  }
})
.then(function (response) {
  console.log(response);
})
.catch(function (error) {
  console.log(error);
});

这就是使用TypeScript从零重构axios的过程。