自己制作 js ajax 请求类(4)

                open(method, url, true);  
                //对于使用POST请求方式  
                if (method == "POST")  
                {  
                    // 设定请求头  
                    setRequestHeader('Content-Type',   
                        'application/x-www-form-urlencoded');  
                    send(data);  
                }  
                //对于采用GET请求  
                if (method == "GET")  
                {  
                    send(null);  
                }  
                //设置状态改变的回调函数  
                onreadystatechange = function ()  
                {  
                    //当服务器的相应完成时，以及获得了正常的服务器响应  
                    if (objXMLHttp.readyState == 4 &&  
                        (objXMLHttp.status == 200 ||   
                            objXMLHttp.status == 304))