通过ES6实现的Ajax类

个人学习用途而已，仅供参考。

 class Ajax  {
     constructor(xhr) {
         xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
         this.xhr = xhr;
     }

     send(method, url, async, callback, data) {
         let xhr = this.xhr;

         xhr.onreadystatechange = () => {
             // readyState: 0: init, 1: connect has set up, 2: recive request, 3: request.. , 4: request end, send response
             if (xhr.readyState === 4 && xhr.status === 200) {
                 // status: 200: OK,  404: Not Found Page
                 callback(xhr.responseText);
             }
         };

         xhr.open(method, url, async);
         xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
         xhr.send(data);
     }
 }

Promise增强版:

 class Ajax  {
     constructor(xhr) {
         xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
         this.xhr = xhr;
     }

     send(options) {

         let xhr = this.xhr;

         let opt = {
             type: options.type || 'get',
             url: options.url || '',
             async: options.async || true,
             dataType: options.dataType || 'json',
             questring: options.questring || ''
         };

         return new Promise((resolve, reject) => {

             xhr.open(opt.type, opt.url, opt.async);

             xhr.onreadystatechange = () => {
                 // readyState: 0: init, 1: connect has set up, 2: recive request, 3: request.. , 4: request end, send response
                 if (xhr.readyState === 4) {
                     if (xhr.status === 200) {
                         // status: 200: OK,  404: Not Found Page
                         if (opt.dataType === 'json') {
                             const data = JSON.parse(xhr.responseText);
                             resolve(data);
                         }
                     } else {
                         reject(new Error(xhr.status || 'Server is fail.'));
                     }
                 }
             };

             xhr.onerror = () => {
                 reject(new Error(xhr.status || 'Server is fail.'));
             }

             xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
             xhr.send(opt.questring);

         });
     }
 }

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