完美相容IE、FF、Opera的Ajax類支援get、post、自訂回呼函數

function Ajax(){  this.httpXML=false;  this.init();  }  Ajax.prototype.init=function(){  if(window.XMLHttpRequest){  this.httpXML=new XMLHttpRequest();   if (this.httpXML.overrideMimeType){  this.httpXML.overrideMimeType("text/xml");   }  }else if(window.ActiveXObject){  try{this.httpXML = new ActiveXObject("Msxml2.XMLHTTP");}catch (e){   try{this.httpXML = new ActiveXObject("Microsoft.XMLHTTP");}catch (e){}   }  }  if(!this.httpXML){  window.alert("can't create XMLHttpRequest object");  return null;  }  }  Ajax.prototype.send=function(_method,_url,_data,_callback){  this.httpXML.onreadystatechange=function(){  if(this.readyState==4&&this.status==200){  _callback.call(this,this.responseText);  }  }      if (_method.toLowerCase() == "get"){   this.httpXML.open(_method, _url, true);   this.httpXML.send(null);   }else if (_method.toLowerCase() == "post"){   this.httpXML.open(_method, _url, true);   this.httpXML.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");   this.httpXML.send(_data);   }      }//===========================================function getResult(data){alert(data);}new Ajax().send('post','url','a=1&b=2',getResult);