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【HTML5】【AJAX的几种封装方法详解】

AJAX (Asynchronous JavaScript and XML) 封装是为了简化重复的异步请求代码，提高开发效率和代码复用性。下面我将介绍几种常见的 AJAX 封装方式。

方法1. 基于原生 XMLHttpRequest 的封装

XMLHttpRequest。其主要特点如下：

1. 实现动态不刷新，通过异步⽅式，提升⽤户体验，优化了浏览器和服务器之间的传输。
2. 把⼀部分原本由服务器负担的⼯作转移到客户端，利⽤客户端闲置的资源进⾏处理，减轻服务器和带宽的负担，节约空间和成本。
3. ⽆刷新更新⻚⾯，⽤户不⽤再像以前⼀样在服务器处理数据时，只能在死板的⽩屏前焦急的等待。AJAX使⽤XMLHttpRequest对象发送请求并得到服务器响应，在不需要重新载⼊整个⻚⾯的情况下，就可以通过DOM及时将更新的内容显示在⻚⾯上。

/*** 基于原生XHR的AJAX封装* @param {Object} options 配置对象* @param {string} options.url 请求地址* @param {string} [options.method='GET'] 请求方法* @param {Object} [options.data=null] 请求数据* @param {Object} [options.headers={}] 请求头* @param {function} [options.success] 成功回调* @param {function} [options.error] 失败回调*/
function ajax(options) {const xhr = new XMLHttpRequest();const method = options.method || 'GET';let url = options.url;let data = options.data || null;// 处理GET请求的查询参数if (method === 'GET' && data) {const params = new URLSearchParams();for (const key in data) {params.append(key, data[key]);}url += '?' + params.toString();data = null;}xhr.open(method, url, true);// 设置请求头if (options.headers) {for (const key in options.headers) {xhr.setRequestHeader(key, options.headers[key]);}}xhr.onreadystatechange = function() {if (xhr.readyState === 4) {if (xhr.status >= 200 && xhr.status < 300) {let response = xhr.responseText;try {response = JSON.parse(response);} catch (e) {}options.success && options.success(response);} else {options.error && options.error(xhr.status, xhr.statusText);}}};xhr.onerror = function() {options.error && options.error(-1, 'Network Error');};// 发送请求if (data && typeof data === 'object') {xhr.setRequestHeader('Content-Type', 'application/json');xhr.send(JSON.stringify(data));} else {xhr.send(data);}
}// 使用示例
ajax({url: '/api/user',method: 'POST',data: { name: 'John', age: 30 },headers: {'Authorization': 'Bearer token123'},success: function(response) {console.log('Success:', response);},error: function(status, statusText) {console.error('Error:', status, statusText);}
});

方法2. 基于 Fetch API 的封装

/*** 基于Fetch API的AJAX封装* @param {string} url 请求地址* @param {Object} [options={}] 请求配置* @returns {Promise} 返回Promise对象*/
function fetchAjax(url, options = {}) {const defaultOptions = {method: 'GET',headers: {'Content-Type': 'application/json'},credentials: 'same-origin', // 携带cookie...options};// 处理GET请求的查询参数if (defaultOptions.method === 'GET' && defaultOptions.body) {const params = new URLSearchParams();for (const key in defaultOptions.body) {params.append(key, defaultOptions.body[key]);}url += '?' + params.toString();delete defaultOptions.body;}// 处理非GET请求的body数据if (defaultOptions.body && typeof defaultOptions.body === 'object') {defaultOptions.body = JSON.stringify(defaultOptions.body);}return fetch(url, defaultOptions).then(async response => {const data = await response.json().catch(() => ({}));if (!response.ok) {const error = new Error(response.statusText);error.response = response;error.data = data;throw error;}return data;});
}// 使用示例
fetchAjax('/api/user', {method: 'POST',body: { name: 'John', age: 30 },headers: {'Authorization': 'Bearer token123'}
})
.then(data => console.log('Success:', data))
.catch(err => console.error('Error:', err));

方法 3. 基于 Axios 风格的封装

class Ajax {constructor(baseURL = '', timeout = 10000) {this.baseURL = baseURL;this.timeout = timeout;this.interceptors = {request: [],response: []};}request(config) {// 处理请求拦截器let chain = [this._dispatchRequest, undefined];this.interceptors.request.forEach(interceptor => {chain.unshift(interceptor.fulfilled, interceptor.rejected);});this.interceptors.response.forEach(interceptor => {chain.push(interceptor.fulfilled, interceptor.rejected);});let promise = Promise.resolve(config);while (chain.length) {promise = promise.then(chain.shift(), chain.shift());}return promise;}_dispatchRequest(config) {return new Promise((resolve, reject) => {const xhr = new XMLHttpRequest();let url = config.baseURL ? config.baseURL + config.url : config.url;let data = config.data;// 处理GET请求参数if (config.method === 'GET' && data) {const params = new URLSearchParams();for (const key in data) {params.append(key, data[key]);}url += '?' + params.toString();data = null;}xhr.timeout = config.timeout || 10000;xhr.open(config.method, url, true);// 设置请求头if (config.headers) {for (const key in config.headers) {xhr.setRequestHeader(key, config.headers[key]);}}xhr.onload = function() {if (xhr.status >= 200 && xhr.status < 300) {let response = xhr.responseText;try {response = JSON.parse(response);} catch (e) {}resolve({data: response,status: xhr.status,statusText: xhr.statusText,headers: xhr.getAllResponseHeaders()});} else {reject(new Error(`Request failed with status code ${xhr.status}`));}};xhr.onerror = function() {reject(new Error('Network Error'));};xhr.ontimeout = function() {reject(new Error('Timeout'));};// 发送请求if (data && typeof data === 'object') {xhr.setRequestHeader('Content-Type', 'application/json');xhr.send(JSON.stringify(data));} else {xhr.send(data);}});}get(url, config = {}) {return this.request({...config,method: 'GET',url});}post(url, data, config = {}) {return this.request({...config,method: 'POST',url,data});}// 添加拦截器useRequestInterceptor(fulfilled, rejected) {this.interceptors.request.push({ fulfilled, rejected });return this.interceptors.request.length - 1;}useResponseInterceptor(fulfilled, rejected) {this.interceptors.response.push({ fulfilled, rejected });return this.interceptors.response.length - 1;}// 移除拦截器ejectRequestInterceptor(id) {if (this.interceptors.request[id]) {this.interceptors.request.splice(id, 1);}}ejectResponseInterceptor(id) {if (this.interceptors.response[id]) {this.interceptors.response.splice(id, 1);}}
}// 使用示例
const api = new Ajax('https://api.example.com');// 添加请求拦截器
api.useRequestInterceptor(config => {config.headers = config.headers || {};config.headers['Authorization'] = 'Bearer token123';return config;
});// 添加响应拦截器
api.useResponseInterceptor(response => {console.log('Response:', response);return response.data;
}, error => {console.error('Error:', error);return Promise.reject(error);
});// 发起请求
api.get('/user/123').then(data => console.log('User data:', data)).catch(err => console.error('Error:', err));api.post('/user', { name: 'John', age: 30 }).then(data => console.log('Created user:', data)).catch(err => console.error('Error:', err));

4. 封装要点总结

统一接口：提供一致的调用方式，如get(), post()等方法

参数处理：

GET请求自动拼接查询参数

POST请求自动处理Content-Type

拦截器机制：支持请求/响应拦截

错误处理：统一错误处理逻辑

Promise支持：返回Promise便于链式调用

超时处理：设置合理的请求超时时间

扩展性：支持自定义配置和拦截器

5. 实际项目中的增强功能

1.自动重试机制：

function withRetry(fn, retries = 3, delay = 1000) {return function(...args) {return new Promise((resolve, reject) => {function attempt(retryCount) {fn(...args).then(resolve).catch(err => {if (retryCount < retries) {setTimeout(() => attempt(retryCount + 1), delay);} else {reject(err);}});}attempt(0);});};
}// 使用示例
const ajaxWithRetry = withRetry(ajax, 3, 1000);

2.请求取消功能：

function createCancelToken() {let cancel;const token = new Promise((resolve, reject) => {cancel = reject;});return { token, cancel };
}// 在请求中检查取消token
function ajaxWithCancel(options) {const { token, cancel } = createCancelToken();const xhr = new XMLHttpRequest();const promise = new Promise((resolve, reject) => {// ...正常请求逻辑// 检查取消token.catch(err => {xhr.abort();reject(err);});});return { promise, cancel };
}

3.请求缓存：

const cache = new Map();function cachedAjax(options) {const cacheKey = JSON.stringify(options);if (cache.has(cacheKey)) {return Promise.resolve(cache.get(cacheKey));}return ajax(options).then(response => {cache.set(cacheKey, response);return response;});
}

根据项目需求选择合适的封装方式，小型项目可使用简单封装，大型项目建议使用成熟的库如Axios。