Ajax获取xmlHTTPRequest代码

function getXMLRequester( )
{
var xmlhttp_request = false;
try
{
if( window.ActiveXObject )
{
for( var i = 5; i; i-- )
{
try{
if( i == 2 ){xmlhttp_request = new ActiveXObject( "Microsoft.XMLHTTP" );
}
else
{
xmlhttp_request = new ActiveXObject( "Msxml2.XMLHTTP." + i + ".0" );
xmlhttp_request.setRequestHeader("Content-Type","text/xml");xmlhttp_request.setRequestHeader("Content-Type","gb2312");
}
break;}
catch(e){
xmlhttp_request = false;
}
}
}
else if( window.XMLHttpRequest )
{
xmlhttp_request = new XMLHttpRequest();
if (xmlhttp_request.overrideMimeType)
{
xmlhttp_request.overrideMimeType('text/xml');
}
}
}
catch(e)
{
xmlhttp_request = false;
}
return xmlhttp_request ;
}