封装，使用有示例.

1     // 封装示例： 2     function ajax(url, method, params, done) { 3       var xhr = null; 4       method = method.toUpperCase(); 5       xhr = window.XMLHttpRequest ? xhr = window.XMLHttpRequest : xhr = new ActiveXObject('Microsoft.XMLHTTP'); 6  7       if (typeof params === 'object') { 8         var tempArr = []; 9         for (var key in params) {10           var value = params[key];11           tempArr.push(key + '=' + value);12         }13         params = tempArr.join('&');14       }15 16       // GET17       if (method === 'GET') {18         url += '?' + params;19       }20       xhr.open(method, url, false);21 22       // POST23       var data = null;24       if (method === 'POST') {25         xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');26         data = params;27       }28 29       xhr.onreadystatechange = function () {30         if (this.readyState !== 4 && this.status !== 200) return false;31         ongone(this.responseText);32       }33       xhr.send(data);34     }35 36 37     // 调用示例：ajax('get','test.php',{id:123,},ongone)38     ajax('GET', 'test.php', {}, ongone);39 40     var ongone = function (res) {41       console.log('1');42       console.log('2');43       console.log(res);44       console.log('gone!');45     }