转载一个完美兼容IE、FF、Opera的Ajax类支持get、post、自定义回调函数

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"){  
         //if(navigator.userAgent.indexOf("MSIE")<=0){ 
         //     netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead"); 
         //} 
         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);  
    }  
       
} 
   
Ajax.prototype.callback=function(){ 
        
}