xmlhttp=null; else alert("fail to Create XmlhTtp- aJax Disabled! ") function callback if(xmlhttpreadyState==4) If(xmlhttpstatus==200) //204响应码指示服务器没有发回任何信息 elseifxmlhttpstatus==204) function sendRequest ( var url=". Servlet?names="+ escape (input Field. value); mlhttp.open(“GET”,url,true); xmlhttponreadystatechange=callback xmlhttp.seNd(null);{ xmlHttp = null; } } } else alert ( “Fail to Create XMLHttp – Ajax Disabled!” ); } function callback ( ) { if ( xmlHttp.readyState == 4 ) { If ( xmlHttp.status == 200 ) { … } //204响应码指示服务器没有发回任何信息 else if ( xmlHttp.status == 204 ) { … } } } function sendRequest ( ) { … var url = “…Servlet?names=” + escape (inputField.value) ; xmlHttp.open ( “GET”, url, true ); xmlHttp.onreadystatechange = callback; xmlHttp.send ( null ); … }