我想知道为什么这段代码适用于firefox、chrome和IE10，但不适用于IE9varajaxReq=newXMLHttpRequest();varparams="name="+$('#name').val()varurl="register.php";ajaxReq.open("POST",url,true);ajaxReq.setRequestHeader("Content-type","application/x-www-form-urlencoded");ajaxReq.setRequestHeader("Content-length",params.length);aja